LibSQL: Parse most language expressions

https://sqlite.org/lang_expr.html

The entry point to using expressions, parse_expression(), is not used
by SQL::Parser in this commit. But there's so much here that it's easier
to grok as its own commit.

5 files changed, 1414 insertions, 5 deletions

diff --git a/Userland/Libraries/LibSQL/AST.h b/Userland/Libraries/LibSQL/AST.h
index 74d2619eb7..e90fcb7777 100644
--- a/Userland/Libraries/LibSQL/AST.h
+++ b/Userland/Libraries/LibSQL/AST.h
@@ -29,7 +29,10 @@
 #include <AK/NonnullRefPtr.h>
 #include <AK/NonnullRefPtrVector.h>
 #include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
 #include <AK/String.h>
+#include <LibSQL/Forward.h>
+#include <LibSQL/Token.h>
 
 namespace SQL {
 
@@ -48,11 +51,9 @@ protected:
     ASTNode() = default;
 };
 
-class Statement : public ASTNode {
-};
-
-class ErrorStatement final : public Statement {
-};
+//==================================================================================================
+// Language types
+//==================================================================================================
 
 class SignedNumber final : public ASTNode {
 public:
@@ -100,6 +101,356 @@ private:
     NonnullRefPtr<TypeName> m_type_name;
 };
 
+//==================================================================================================
+// Expressions
+//==================================================================================================
+
+class Expression : public ASTNode {
+};
+
+class ErrorExpression final : public Expression {
+};
+
+class NumericLiteral : public Expression {
+public:
+    explicit NumericLiteral(double value)
+        : m_value(value)
+    {
+    }
+
+    double value() const { return m_value; }
+
+private:
+    double m_value;
+};
+
+class StringLiteral : public Expression {
+public:
+    explicit StringLiteral(String value)
+        : m_value(move(value))
+    {
+    }
+
+    const String& value() const { return m_value; }
+
+private:
+    String m_value;
+};
+
+class BlobLiteral : public Expression {
+public:
+    explicit BlobLiteral(String value)
+        : m_value(move(value))
+    {
+    }
+
+    const String& value() const { return m_value; }
+
+private:
+    String m_value;
+};
+
+class NullLiteral : public Expression {
+};
+
+class NestedExpression : public Expression {
+public:
+    const NonnullRefPtr<Expression>& expression() const { return m_expression; }
+
+protected:
+    explicit NestedExpression(NonnullRefPtr<Expression> expression)
+        : m_expression(move(expression))
+    {
+    }
+
+private:
+    NonnullRefPtr<Expression> m_expression;
+};
+
+class NestedDoubleExpression : public Expression {
+public:
+    const NonnullRefPtr<Expression>& lhs() const { return m_lhs; }
+    const NonnullRefPtr<Expression>& rhs() const { return m_rhs; }
+
+protected:
+    NestedDoubleExpression(NonnullRefPtr<Expression> lhs, NonnullRefPtr<Expression> rhs)
+        : m_lhs(move(lhs))
+        , m_rhs(move(rhs))
+    {
+    }
+
+private:
+    NonnullRefPtr<Expression> m_lhs;
+    NonnullRefPtr<Expression> m_rhs;
+};
+
+class InvertibleNestedExpression : public NestedExpression {
+public:
+    bool invert_expression() const { return m_invert_expression; }
+
+protected:
+    InvertibleNestedExpression(NonnullRefPtr<Expression> expression, bool invert_expression)
+        : NestedExpression(move(expression))
+        , m_invert_expression(invert_expression)
+    {
+    }
+
+private:
+    bool m_invert_expression;
+};
+
+class InvertibleNestedDoubleExpression : public NestedDoubleExpression {
+public:
+    bool invert_expression() const { return m_invert_expression; }
+
+protected:
+    InvertibleNestedDoubleExpression(NonnullRefPtr<Expression> lhs, NonnullRefPtr<Expression> rhs, bool invert_expression)
+        : NestedDoubleExpression(move(lhs), move(rhs))
+        , m_invert_expression(invert_expression)
+    {
+    }
+
+private:
+    bool m_invert_expression;
+};
+
+class ColumnNameExpression : public Expression {
+public:
+    ColumnNameExpression(String schema_name, String table_name, String column_name)
+        : m_schema_name(move(schema_name))
+        , m_table_name(move(table_name))
+        , m_column_name(move(column_name))
+    {
+    }
+
+    const String& schema_name() const { return m_schema_name; }
+    const String& table_name() const { return m_table_name; }
+    const String& column_name() const { return m_column_name; }
+
+private:
+    String m_schema_name;
+    String m_table_name;
+    String m_column_name;
+};
+
+enum class UnaryOperator {
+    Minus,
+    Plus,
+    BitwiseNot,
+    Not,
+};
+
+class UnaryOperatorExpression : public NestedExpression {
+public:
+    UnaryOperatorExpression(UnaryOperator type, NonnullRefPtr<Expression> expression)
+        : NestedExpression(move(expression))
+        , m_type(type)
+    {
+    }
+
+    UnaryOperator type() const { return m_type; }
+
+private:
+    UnaryOperator m_type;
+};
+
+enum class BinaryOperator {
+    // Note: These are in order of highest-to-lowest operator precedence.
+    Concatenate,
+    Multiplication,
+    Division,
+    Modulo,
+    Plus,
+    Minus,
+    ShiftLeft,
+    ShiftRight,
+    BitwiseAnd,
+    BitwiseOr,
+    LessThan,
+    LessThanEquals,
+    GreaterThan,
+    GreaterThanEquals,
+    Equals,
+    NotEquals,
+    And,
+    Or,
+};
+
+class BinaryOperatorExpression : public NestedDoubleExpression {
+public:
+    BinaryOperatorExpression(BinaryOperator type, NonnullRefPtr<Expression> lhs, NonnullRefPtr<Expression> rhs)
+        : NestedDoubleExpression(move(lhs), move(rhs))
+        , m_type(type)
+    {
+    }
+
+    BinaryOperator type() const { return m_type; }
+
+private:
+    BinaryOperator m_type;
+};
+
+class ChainedExpression : public Expression {
+public:
+    explicit ChainedExpression(NonnullRefPtrVector<Expression> expressions)
+        : m_expressions(move(expressions))
+    {
+    }
+
+    const NonnullRefPtrVector<Expression>& expressions() const { return m_expressions; }
+
+private:
+    NonnullRefPtrVector<Expression> m_expressions;
+};
+
+class CastExpression : public NestedExpression {
+public:
+    CastExpression(NonnullRefPtr<Expression> expression, NonnullRefPtr<TypeName> type_name)
+        : NestedExpression(move(expression))
+        , m_type_name(move(type_name))
+    {
+    }
+
+    const NonnullRefPtr<TypeName>& type_name() const { return m_type_name; }
+
+private:
+    NonnullRefPtr<TypeName> m_type_name;
+};
+
+class CaseExpression : public Expression {
+public:
+    struct WhenThenClause {
+        NonnullRefPtr<Expression> when;
+        NonnullRefPtr<Expression> then;
+    };
+
+    CaseExpression(RefPtr<Expression> case_expression, Vector<WhenThenClause> when_then_clauses, RefPtr<Expression> else_expression)
+        : m_case_expression(case_expression)
+        , m_when_then_clauses(when_then_clauses)
+        , m_else_expression(else_expression)
+    {
+        VERIFY(!m_when_then_clauses.is_empty());
+    }
+
+    const RefPtr<Expression>& case_expression() const { return m_case_expression; }
+    const Vector<WhenThenClause>& when_then_clauses() const { return m_when_then_clauses; }
+    const RefPtr<Expression>& else_expression() const { return m_else_expression; }
+
+private:
+    RefPtr<Expression> m_case_expression;
+    Vector<WhenThenClause> m_when_then_clauses;
+    RefPtr<Expression> m_else_expression;
+};
+
+class CollateExpression : public NestedExpression {
+public:
+    CollateExpression(NonnullRefPtr<Expression> expression, String collation_name)
+        : NestedExpression(move(expression))
+        , m_collation_name(move(collation_name))
+    {
+    }
+
+    const String& collation_name() const { return m_collation_name; }
+
+private:
+    String m_collation_name;
+};
+
+enum class MatchOperator {
+    Like,
+    Glob,
+    Match,
+    Regexp,
+};
+
+class MatchExpression : public InvertibleNestedDoubleExpression {
+public:
+    MatchExpression(MatchOperator type, NonnullRefPtr<Expression> lhs, NonnullRefPtr<Expression> rhs, RefPtr<Expression> escape, bool invert_expression)
+        : InvertibleNestedDoubleExpression(move(lhs), move(rhs), invert_expression)
+        , m_type(type)
+        , m_escape(move(escape))
+    {
+    }
+
+    MatchOperator type() const { return m_type; }
+    const RefPtr<Expression>& escape() const { return m_escape; }
+
+private:
+    MatchOperator m_type;
+    RefPtr<Expression> m_escape;
+};
+
+class NullExpression : public InvertibleNestedExpression {
+public:
+    NullExpression(NonnullRefPtr<Expression> expression, bool invert_expression)
+        : InvertibleNestedExpression(move(expression), invert_expression)
+    {
+    }
+};
+
+class IsExpression : public InvertibleNestedDoubleExpression {
+public:
+    IsExpression(NonnullRefPtr<Expression> lhs, NonnullRefPtr<Expression> rhs, bool invert_expression)
+        : InvertibleNestedDoubleExpression(move(lhs), move(rhs), invert_expression)
+    {
+    }
+};
+
+class BetweenExpression : public InvertibleNestedDoubleExpression {
+public:
+    BetweenExpression(NonnullRefPtr<Expression> expression, NonnullRefPtr<Expression> lhs, NonnullRefPtr<Expression> rhs, bool invert_expression)
+        : InvertibleNestedDoubleExpression(move(lhs), move(rhs), invert_expression)
+        , m_expression(move(expression))
+    {
+    }
+
+    const NonnullRefPtr<Expression>& expression() const { return m_expression; }
+
+private:
+    NonnullRefPtr<Expression> m_expression;
+};
+
+class InChainedExpression : public InvertibleNestedExpression {
+public:
+    InChainedExpression(NonnullRefPtr<Expression> expression, NonnullRefPtr<ChainedExpression> expression_chain, bool invert_expression)
+        : InvertibleNestedExpression(move(expression), invert_expression)
+        , m_expression_chain(move(expression_chain))
+    {
+    }
+
+    const NonnullRefPtr<ChainedExpression>& expression_chain() const { return m_expression_chain; }
+
+private:
+    NonnullRefPtr<ChainedExpression> m_expression_chain;
+};
+
+class InTableExpression : public InvertibleNestedExpression {
+public:
+    InTableExpression(NonnullRefPtr<Expression> expression, String schema_name, String table_name, bool invert_expression)
+        : InvertibleNestedExpression(move(expression), invert_expression)
+        , m_schema_name(move(schema_name))
+        , m_table_name(move(table_name))
+    {
+    }
+
+    const String& schema_name() const { return m_schema_name; }
+    const String& table_name() const { return m_table_name; }
+
+private:
+    String m_schema_name;
+    String m_table_name;
+};
+
+//==================================================================================================
+// Statements
+//==================================================================================================
+
+class Statement : public ASTNode {
+};
+
+class ErrorStatement final : public Statement {
+};
+
 class CreateTable : public Statement {
 public:
     CreateTable(String schema_name, String table_name, NonnullRefPtrVector<ColumnDefinition> columns, bool is_temporary, bool is_error_if_table_exists)
diff --git a/Userland/Libraries/LibSQL/Forward.h b/Userland/Libraries/LibSQL/Forward.h
index b27e83a158..0430a97bb5 100644
--- a/Userland/Libraries/LibSQL/Forward.h
+++ b/Userland/Libraries/LibSQL/Forward.h
@@ -28,14 +28,37 @@
 
 namespace SQL {
 class ASTNode;
+class BetweenExpression;
+class BinaryOperatorExpression;
+class BlobLiteral;
+class CaseExpression;
+class CastExpression;
+class ChainedExpression;
+class CollateExpression;
 class ColumnDefinition;
+class ColumnNameExpression;
 class CreateTable;
 class DropTable;
+class ErrorExpression;
 class ErrorStatement;
+class Expression;
+class InChainedExpression;
+class InTableExpression;
+class InvertibleNestedDoubleExpression;
+class InvertibleNestedExpression;
+class IsExpression;
 class Lexer;
+class MatchExpression;
+class NestedDoubleExpression;
+class NestedExpression;
+class NullExpression;
+class NullLiteral;
+class NumericLiteral;
 class Parser;
 class SignedNumber;
 class Statement;
+class StringLiteral;
 class Token;
 class TypeName;
+class UnaryOperatorExpression;
 }
diff --git a/Userland/Libraries/LibSQL/Parser.cpp b/Userland/Libraries/LibSQL/Parser.cpp
index fb25d1cddd..e35398db15 100644
--- a/Userland/Libraries/LibSQL/Parser.cpp
+++ b/Userland/Libraries/LibSQL/Parser.cpp
@@ -25,6 +25,7 @@
  */
 
 #include "Parser.h"
+#include <AK/TypeCasts.h>
 
 namespace SQL {
 
@@ -124,6 +125,449 @@ NonnullRefPtr<DropTable> Parser::parse_drop_table_statement()
     return create_ast_node<DropTable>(move(schema_name), move(table_name), is_error_if_table_does_not_exist);
 }
 
+NonnullRefPtr<Expression> Parser::parse_expression()
+{
+    // https://sqlite.org/lang_expr.html
+    auto expression = parse_primary_expression();
+
+    if (match_secondary_expression())
+        expression = parse_secondary_expression(move(expression));
+
+    // FIXME: Parse 'bind-parameter'.
+    // FIXME: Parse 'function-name'.
+    // FIXME: Parse 'exists'.
+    // FIXME: Parse 'raise-function'.
+
+    return expression;
+}
+
+NonnullRefPtr<Expression> Parser::parse_primary_expression()
+{
+    if (auto expression = parse_literal_value_expression(); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_column_name_expression(); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_unary_operator_expression(); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_chained_expression(); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_cast_expression(); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_case_expression(); expression.has_value())
+        return move(expression.value());
+
+    expected("Primary Expression");
+    consume();
+
+    return create_ast_node<ErrorExpression>();
+}
+
+NonnullRefPtr<Expression> Parser::parse_secondary_expression(NonnullRefPtr<Expression> primary)
+{
+    if (auto expression = parse_binary_operator_expression(primary); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_collate_expression(primary); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_is_expression(primary); expression.has_value())
+        return move(expression.value());
+
+    bool invert_expression = false;
+    if (consume_if(TokenType::Not))
+        invert_expression = true;
+
+    if (auto expression = parse_match_expression(primary, invert_expression); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_null_expression(primary, invert_expression); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_between_expression(primary, invert_expression); expression.has_value())
+        return move(expression.value());
+
+    if (auto expression = parse_in_expression(primary, invert_expression); expression.has_value())
+        return move(expression.value());
+
+    expected("Secondary Expression");
+    consume();
+
+    return create_ast_node<ErrorExpression>();
+}
+
+bool Parser::match_secondary_expression() const
+{
+    return match(TokenType::Not)
+        || match(TokenType::DoublePipe)
+        || match(TokenType::Asterisk)
+        || match(TokenType::Divide)
+        || match(TokenType::Modulus)
+        || match(TokenType::Plus)
+        || match(TokenType::Minus)
+        || match(TokenType::ShiftLeft)
+        || match(TokenType::ShiftRight)
+        || match(TokenType::Ampersand)
+        || match(TokenType::Pipe)
+        || match(TokenType::LessThan)
+        || match(TokenType::LessThanEquals)
+        || match(TokenType::GreaterThan)
+        || match(TokenType::GreaterThanEquals)
+        || match(TokenType::Equals)
+        || match(TokenType::EqualsEquals)
+        || match(TokenType::NotEquals1)
+        || match(TokenType::NotEquals2)
+        || match(TokenType::And)
+        || match(TokenType::Or)
+        || match(TokenType::Collate)
+        || match(TokenType::Is)
+        || match(TokenType::Like)
+        || match(TokenType::Glob)
+        || match(TokenType::Match)
+        || match(TokenType::Regexp)
+        || match(TokenType::Isnull)
+        || match(TokenType::Notnull)
+        || match(TokenType::Between)
+        || match(TokenType::In);
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_literal_value_expression()
+{
+    if (match(TokenType::NumericLiteral)) {
+        auto value = consume().double_value();
+        return create_ast_node<NumericLiteral>(value);
+    }
+    if (match(TokenType::StringLiteral)) {
+        // TODO: Should the surrounding ' ' be removed here?
+        auto value = consume().value();
+        return create_ast_node<StringLiteral>(value);
+    }
+    if (match(TokenType::BlobLiteral)) {
+        // TODO: Should the surrounding x' ' be removed here?
+        auto value = consume().value();
+        return create_ast_node<BlobLiteral>(value);
+    }
+    if (consume_if(TokenType::Null))
+        return create_ast_node<NullLiteral>();
+
+    return {};
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_column_name_expression()
+{
+    if (!match(TokenType::Identifier))
+        return {};
+
+    String first_identifier = consume(TokenType::Identifier).value();
+    String schema_name;
+    String table_name;
+    String column_name;
+
+    if (consume_if(TokenType::Period)) {
+        String second_identifier = consume(TokenType::Identifier).value();
+
+        if (consume_if(TokenType::Period)) {
+            schema_name = move(first_identifier);
+            table_name = move(second_identifier);
+            column_name = consume(TokenType::Identifier).value();
+        } else {
+            table_name = move(first_identifier);
+            column_name = move(second_identifier);
+        }
+    } else {
+        column_name = move(first_identifier);
+    }
+
+    return create_ast_node<ColumnNameExpression>(move(schema_name), move(table_name), move(column_name));
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_unary_operator_expression()
+{
+    if (consume_if(TokenType::Minus))
+        return create_ast_node<UnaryOperatorExpression>(UnaryOperator::Minus, parse_expression());
+
+    if (consume_if(TokenType::Plus))
+        return create_ast_node<UnaryOperatorExpression>(UnaryOperator::Plus, parse_expression());
+
+    if (consume_if(TokenType::Tilde))
+        return create_ast_node<UnaryOperatorExpression>(UnaryOperator::BitwiseNot, parse_expression());
+
+    if (consume_if(TokenType::Not))
+        return create_ast_node<UnaryOperatorExpression>(UnaryOperator::Not, parse_expression());
+
+    return {};
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_binary_operator_expression(NonnullRefPtr<Expression> lhs)
+{
+    if (consume_if(TokenType::DoublePipe))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Concatenate, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Asterisk))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Multiplication, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Divide))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Division, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Modulus))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Modulo, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Plus))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Plus, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Minus))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Minus, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::ShiftLeft))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::ShiftLeft, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::ShiftRight))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::ShiftRight, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Ampersand))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::BitwiseAnd, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Pipe))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::BitwiseOr, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::LessThan))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::LessThan, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::LessThanEquals))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::LessThanEquals, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::GreaterThan))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::GreaterThan, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::GreaterThanEquals))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::GreaterThanEquals, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Equals) || consume_if(TokenType::EqualsEquals))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Equals, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::NotEquals1) || consume_if(TokenType::NotEquals2))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::NotEquals, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::And))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::And, move(lhs), parse_expression());
+
+    if (consume_if(TokenType::Or))
+        return create_ast_node<BinaryOperatorExpression>(BinaryOperator::Or, move(lhs), parse_expression());
+
+    return {};
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_chained_expression()
+{
+    if (!match(TokenType::ParenOpen))
+        return {};
+
+    NonnullRefPtrVector<Expression> expressions;
+    consume(TokenType::ParenOpen);
+
+    do {
+        expressions.append(parse_expression());
+        if (match(TokenType::ParenClose))
+            break;
+
+        consume(TokenType::Comma);
+    } while (!match(TokenType::Eof));
+
+    consume(TokenType::ParenClose);
+
+    return create_ast_node<ChainedExpression>(move(expressions));
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_cast_expression()
+{
+    if (!match(TokenType::Cast))
+        return {};
+
+    consume(TokenType::Cast);
+    consume(TokenType::ParenOpen);
+    auto expression = parse_expression();
+    consume(TokenType::As);
+    auto type_name = parse_type_name();
+    consume(TokenType::ParenClose);
+
+    return create_ast_node<CastExpression>(move(expression), move(type_name));
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_case_expression()
+{
+    if (!match(TokenType::Case))
+        return {};
+
+    consume();
+
+    RefPtr<Expression> case_expression;
+    if (!match(TokenType::When)) {
+        case_expression = parse_expression();
+    }
+
+    Vector<CaseExpression::WhenThenClause> when_then_clauses;
+
+    do {
+        consume(TokenType::When);
+        auto when = parse_expression();
+        consume(TokenType::Then);
+        auto then = parse_expression();
+
+        when_then_clauses.append({ move(when), move(then) });
+
+        if (!match(TokenType::When))
+            break;
+    } while (!match(TokenType::Eof));
+
+    RefPtr<Expression> else_expression;
+    if (consume_if(TokenType::Else))
+        else_expression = parse_expression();
+
+    consume(TokenType::End);
+    return create_ast_node<CaseExpression>(move(case_expression), move(when_then_clauses), move(else_expression));
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_collate_expression(NonnullRefPtr<Expression> expression)
+{
+    if (!match(TokenType::Collate))
+        return {};
+
+    consume();
+    String collation_name = consume(TokenType::Identifier).value();
+
+    return create_ast_node<CollateExpression>(move(expression), move(collation_name));
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_is_expression(NonnullRefPtr<Expression> expression)
+{
+    if (!match(TokenType::Is))
+        return {};
+
+    consume();
+
+    bool invert_expression = false;
+    if (match(TokenType::Not)) {
+        consume();
+        invert_expression = true;
+    }
+
+    auto rhs = parse_expression();
+    return create_ast_node<IsExpression>(move(expression), move(rhs), invert_expression);
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_match_expression(NonnullRefPtr<Expression> lhs, bool invert_expression)
+{
+    auto parse_escape = [this]() {
+        RefPtr<Expression> escape;
+        if (consume_if(TokenType::Escape))
+            escape = parse_expression();
+        return escape;
+    };
+
+    if (consume_if(TokenType::Like))
+        return create_ast_node<MatchExpression>(MatchOperator::Like, move(lhs), parse_expression(), parse_escape(), invert_expression);
+
+    if (consume_if(TokenType::Glob))
+        return create_ast_node<MatchExpression>(MatchOperator::Glob, move(lhs), parse_expression(), parse_escape(), invert_expression);
+
+    if (consume_if(TokenType::Match))
+        return create_ast_node<MatchExpression>(MatchOperator::Match, move(lhs), parse_expression(), parse_escape(), invert_expression);
+
+    if (consume_if(TokenType::Regexp))
+        return create_ast_node<MatchExpression>(MatchOperator::Regexp, move(lhs), parse_expression(), parse_escape(), invert_expression);
+
+    return {};
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_null_expression(NonnullRefPtr<Expression> expression, bool invert_expression)
+{
+    if (!match(TokenType::Isnull) && !match(TokenType::Notnull) && !(invert_expression && match(TokenType::Null)))
+        return {};
+
+    auto type = consume().type();
+    invert_expression |= (type == TokenType::Notnull);
+
+    return create_ast_node<NullExpression>(move(expression), invert_expression);
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_between_expression(NonnullRefPtr<Expression> expression, bool invert_expression)
+{
+    if (!match(TokenType::Between))
+        return {};
+
+    consume();
+
+    auto nested = parse_expression();
+    if (!is<BinaryOperatorExpression>(*nested)) {
+        expected("Binary Expression");
+        return create_ast_node<ErrorExpression>();
+    }
+
+    const auto& binary_expression = static_cast<const BinaryOperatorExpression&>(*nested);
+    if (binary_expression.type() != BinaryOperator::And) {
+        expected("AND Expression");
+        return create_ast_node<ErrorExpression>();
+    }
+
+    return create_ast_node<BetweenExpression>(move(expression), binary_expression.lhs(), binary_expression.rhs(), invert_expression);
+}
+
+Optional<NonnullRefPtr<Expression>> Parser::parse_in_expression(NonnullRefPtr<Expression> expression, bool invert_expression)
+{
+    if (!match(TokenType::In))
+        return {};
+
+    consume();
+
+    if (consume_if(TokenType::ParenOpen)) {
+        if (match(TokenType::Select)) {
+            // FIXME: Parse "select-stmt".
+            return {};
+        }
+
+        // FIXME: Consolidate this with parse_chained_expression(). That method consumes the opening paren as
+        //        well, and also requires at least one expression (whereas this allows for an empty chain).
+        NonnullRefPtrVector<Expression> expressions;
+
+        if (!match(TokenType::ParenClose)) {
+            do {
+                expressions.append(parse_expression());
+                if (match(TokenType::ParenClose))
+                    break;
+
+                consume(TokenType::Comma);
+            } while (!match(TokenType::Eof));
+        }
+
+        consume(TokenType::ParenClose);
+
+        auto chain = create_ast_node<ChainedExpression>(move(expressions));
+        return create_ast_node<InChainedExpression>(move(expression), move(chain), invert_expression);
+    }
+
+    String schema_or_table_name = consume(TokenType::Identifier).value();
+    String schema_name;
+    String table_name;
+
+    if (consume_if(TokenType::Period)) {
+        schema_name = move(schema_or_table_name);
+        table_name = consume(TokenType::Identifier).value();
+    } else {
+        table_name = move(schema_or_table_name);
+    }
+
+    if (match(TokenType::ParenOpen)) {
+        // FIXME: Parse "table-function".
+        return {};
+    }
+
+    return create_ast_node<InTableExpression>(move(expression), move(schema_name), move(table_name), invert_expression);
+}
+
 NonnullRefPtr<ColumnDefinition> Parser::parse_column_definition()
 {
     // https://sqlite.org/syntax/column-def.html
diff --git a/Userland/Libraries/LibSQL/Parser.h b/Userland/Libraries/LibSQL/Parser.h
index 26fb7d2a36..9b0ea5d2ab 100644
--- a/Userland/Libraries/LibSQL/Parser.h
+++ b/Userland/Libraries/LibSQL/Parser.h
@@ -58,6 +58,9 @@ public:
     bool has_errors() const { return m_parser_state.m_errors.size(); }
     const Vector<Error>& errors() const { return m_parser_state.m_errors; }
 
+protected:
+    NonnullRefPtr<Expression> parse_expression(); // Protected for unit testing.
+
 private:
     struct ParserState {
         explicit ParserState(Lexer);
@@ -69,6 +72,24 @@ private:
 
     NonnullRefPtr<CreateTable> parse_create_table_statement();
     NonnullRefPtr<DropTable> parse_drop_table_statement();
+
+    NonnullRefPtr<Expression> parse_primary_expression();
+    NonnullRefPtr<Expression> parse_secondary_expression(NonnullRefPtr<Expression> primary);
+    bool match_secondary_expression() const;
+    Optional<NonnullRefPtr<Expression>> parse_literal_value_expression();
+    Optional<NonnullRefPtr<Expression>> parse_column_name_expression();
+    Optional<NonnullRefPtr<Expression>> parse_unary_operator_expression();
+    Optional<NonnullRefPtr<Expression>> parse_binary_operator_expression(NonnullRefPtr<Expression> lhs);
+    Optional<NonnullRefPtr<Expression>> parse_chained_expression();
+    Optional<NonnullRefPtr<Expression>> parse_cast_expression();
+    Optional<NonnullRefPtr<Expression>> parse_case_expression();
+    Optional<NonnullRefPtr<Expression>> parse_collate_expression(NonnullRefPtr<Expression> expression);
+    Optional<NonnullRefPtr<Expression>> parse_is_expression(NonnullRefPtr<Expression> expression);
+    Optional<NonnullRefPtr<Expression>> parse_match_expression(NonnullRefPtr<Expression> lhs, bool invert_expression);
+    Optional<NonnullRefPtr<Expression>> parse_null_expression(NonnullRefPtr<Expression> expression, bool invert_expression);
+    Optional<NonnullRefPtr<Expression>> parse_between_expression(NonnullRefPtr<Expression> expression, bool invert_expression);
+    Optional<NonnullRefPtr<Expression>> parse_in_expression(NonnullRefPtr<Expression> expression, bool invert_expression);
+
     NonnullRefPtr<ColumnDefinition> parse_column_definition();
     NonnullRefPtr<TypeName> parse_type_name();
     NonnullRefPtr<SignedNumber> parse_signed_number();
diff --git a/Userland/Libraries/LibSQL/Tests/TestSqlExpressionParser.cpp b/Userland/Libraries/LibSQL/Tests/TestSqlExpressionParser.cpp
new file mode 100644
index 0000000000..da3f78974f
--- /dev/null
+++ b/Userland/Libraries/LibSQL/Tests/TestSqlExpressionParser.cpp
@@ -0,0 +1,570 @@
+/*
+ * Copyright (c) 2021, Tim Flynn <trflynn89@pm.me>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/TestSuite.h>
+
+#include <AK/HashMap.h>
+#include <AK/Result.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <AK/StringView.h>
+#include <AK/TypeCasts.h>
+#include <LibSQL/Lexer.h>
+#include <LibSQL/Parser.h>
+
+namespace {
+
+class ExpressionParser : public SQL::Parser {
+public:
+    explicit ExpressionParser(SQL::Lexer lexer)
+        : SQL::Parser(move(lexer))
+    {
+    }
+
+    NonnullRefPtr<SQL::Expression> parse()
+    {
+        return SQL::Parser::parse_expression();
+    }
+};
+
+using ParseResult = AK::Result<NonnullRefPtr<SQL::Expression>, String>;
+
+ParseResult parse(StringView sql)
+{
+    auto parser = ExpressionParser(SQL::Lexer(sql));
+    auto expression = parser.parse();
+
+    if (parser.has_errors()) {
+        return parser.errors()[0].to_string();
+    }
+
+    return expression;
+}
+
+}
+
+TEST_CASE(numeric_literal)
+{
+    auto validate = [](StringView sql, double expected_value) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::NumericLiteral>(*expression));
+
+        const auto& literal = static_cast<const SQL::NumericLiteral&>(*expression);
+        EXPECT_EQ(literal.value(), expected_value);
+    };
+
+    validate("123", 123);
+    validate("3.14", 3.14);
+    validate("0xff", 255);
+    validate("1e3", 1000);
+}
+
+TEST_CASE(string_literal)
+{
+    EXPECT(parse("'").is_error());
+    EXPECT(parse("'unterminated").is_error());
+
+    auto validate = [](StringView sql, StringView expected_value) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::StringLiteral>(*expression));
+
+        const auto& literal = static_cast<const SQL::StringLiteral&>(*expression);
+        EXPECT_EQ(literal.value(), expected_value);
+    };
+
+    validate("''", "''");
+    validate("'hello friends'", "'hello friends'");
+}
+
+TEST_CASE(blob_literal)
+{
+    EXPECT(parse("x'").is_error());
+    EXPECT(parse("x'unterminated").is_error());
+
+    auto validate = [](StringView sql, StringView expected_value) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::BlobLiteral>(*expression));
+
+        const auto& literal = static_cast<const SQL::BlobLiteral&>(*expression);
+        EXPECT_EQ(literal.value(), expected_value);
+    };
+
+    validate("x''", "x''");
+    validate("x'hello friends'", "x'hello friends'");
+}
+
+TEST_CASE(null_literal)
+{
+    auto validate = [](StringView sql) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::NullLiteral>(*expression));
+    };
+
+    validate("NULL");
+}
+
+TEST_CASE(column_name)
+{
+    EXPECT(parse(".column").is_error());
+    EXPECT(parse("table.").is_error());
+    EXPECT(parse("schema.table.").is_error());
+
+    auto validate = [](StringView sql, StringView expected_schema, StringView expected_table, StringView expected_column) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::ColumnNameExpression>(*expression));
+
+        const auto& column = static_cast<const SQL::ColumnNameExpression&>(*expression);
+        EXPECT_EQ(column.schema_name(), expected_schema);
+        EXPECT_EQ(column.table_name(), expected_table);
+        EXPECT_EQ(column.column_name(), expected_column);
+    };
+
+    validate("column", {}, {}, "column");
+    validate("table.column", {}, "table", "column");
+    validate("schema.table.column", "schema", "table", "column");
+}
+
+TEST_CASE(unary_operator)
+{
+    EXPECT(parse("-").is_error());
+    EXPECT(parse("--").is_error());
+    EXPECT(parse("+").is_error());
+    EXPECT(parse("++").is_error());
+    EXPECT(parse("~").is_error());
+    EXPECT(parse("~~").is_error());
+    EXPECT(parse("NOT").is_error());
+
+    auto validate = [](StringView sql, SQL::UnaryOperator expected_operator) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::UnaryOperatorExpression>(*expression));
+
+        const auto& unary = static_cast<const SQL::UnaryOperatorExpression&>(*expression);
+        EXPECT_EQ(unary.type(), expected_operator);
+
+        const auto& secondary_expression = unary.expression();
+        EXPECT(!is<SQL::ErrorExpression>(*secondary_expression));
+    };
+
+    validate("-15", SQL::UnaryOperator::Minus);
+    validate("+15", SQL::UnaryOperator::Plus);
+    validate("~15", SQL::UnaryOperator::BitwiseNot);
+    validate("NOT 15", SQL::UnaryOperator::Not);
+}
+
+TEST_CASE(binary_operator)
+{
+    HashMap<StringView, SQL::BinaryOperator> operators {
+        { "||", SQL::BinaryOperator::Concatenate },
+        { "*", SQL::BinaryOperator::Multiplication },
+        { "/", SQL::BinaryOperator::Division },
+        { "%", SQL::BinaryOperator::Modulo },
+        { "+", SQL::BinaryOperator::Plus },
+        { "-", SQL::BinaryOperator::Minus },
+        { "<<", SQL::BinaryOperator::ShiftLeft },
+        { ">>", SQL::BinaryOperator::ShiftRight },
+        { "&", SQL::BinaryOperator::BitwiseAnd },
+        { "|", SQL::BinaryOperator::BitwiseOr },
+        { "<", SQL::BinaryOperator::LessThan },
+        { "<=", SQL::BinaryOperator::LessThanEquals },
+        { ">", SQL::BinaryOperator::GreaterThan },
+        { ">=", SQL::BinaryOperator::GreaterThanEquals },
+        { "=", SQL::BinaryOperator::Equals },
+        { "==", SQL::BinaryOperator::Equals },
+        { "!=", SQL::BinaryOperator::NotEquals },
+        { "<>", SQL::BinaryOperator::NotEquals },
+        { "AND", SQL::BinaryOperator::And },
+        { "OR", SQL::BinaryOperator::Or },
+    };
+
+    for (auto op : operators) {
+        EXPECT(parse(op.key).is_error());
+
+        StringBuilder builder;
+        builder.append("1 ");
+        builder.append(op.key);
+        EXPECT(parse(builder.build()).is_error());
+
+        builder.clear();
+
+        if (op.key != "+" && op.key != "-") { // "+1" and "-1" are fine (unary operator).
+            builder.append(op.key);
+            builder.append(" 1");
+            EXPECT(parse(builder.build()).is_error());
+        }
+    }
+
+    auto validate = [](StringView sql, SQL::BinaryOperator expected_operator) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::BinaryOperatorExpression>(*expression));
+
+        const auto& binary = static_cast<const SQL::BinaryOperatorExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*binary.lhs()));
+        EXPECT(!is<SQL::ErrorExpression>(*binary.rhs()));
+        EXPECT_EQ(binary.type(), expected_operator);
+    };
+
+    for (auto op : operators) {
+        StringBuilder builder;
+        builder.append("1 ");
+        builder.append(op.key);
+        builder.append(" 1");
+        validate(builder.build(), op.value);
+    }
+}
+
+TEST_CASE(chained_expression)
+{
+    EXPECT(parse("()").is_error());
+    EXPECT(parse("(,)").is_error());
+    EXPECT(parse("(15,)").is_error());
+
+    auto validate = [](StringView sql, size_t expected_chain_size) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::ChainedExpression>(*expression));
+
+        const auto& chain = static_cast<const SQL::ChainedExpression&>(*expression).expressions();
+        EXPECT_EQ(chain.size(), expected_chain_size);
+
+        for (const auto& chained_expression : chain)
+            EXPECT(!is<SQL::ErrorExpression>(chained_expression));
+    };
+
+    validate("(15)", 1);
+    validate("(15, 16)", 2);
+    validate("(15, 16, column)", 3);
+}
+
+TEST_CASE(cast_expression)
+{
+    EXPECT(parse("CAST").is_error());
+    EXPECT(parse("CAST (").is_error());
+    EXPECT(parse("CAST ()").is_error());
+    EXPECT(parse("CAST (15)").is_error());
+    EXPECT(parse("CAST (15 AS").is_error());
+    EXPECT(parse("CAST (15 AS)").is_error());
+    EXPECT(parse("CAST (15 AS int").is_error());
+
+    auto validate = [](StringView sql, StringView expected_type_name) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::CastExpression>(*expression));
+
+        const auto& cast = static_cast<const SQL::CastExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*cast.expression()));
+
+        const auto& type_name = cast.type_name();
+        EXPECT_EQ(type_name->name(), expected_type_name);
+    };
+
+    validate("CAST (15 AS int)", "int");
+    validate("CAST ('NULL' AS null)", "null");
+    validate("CAST (15 AS varchar(255))", "varchar");
+}
+
+TEST_CASE(case_expression)
+{
+    EXPECT(parse("CASE").is_error());
+    EXPECT(parse("CASE END").is_error());
+    EXPECT(parse("CASE 15").is_error());
+    EXPECT(parse("CASE 15 END").is_error());
+    EXPECT(parse("CASE WHEN").is_error());
+    EXPECT(parse("CASE WHEN THEN").is_error());
+    EXPECT(parse("CASE WHEN 15 THEN 16").is_error());
+    EXPECT(parse("CASE WHEN 15 THEN 16 ELSE").is_error());
+    EXPECT(parse("CASE WHEN 15 THEN 16 ELSE END").is_error());
+
+    auto validate = [](StringView sql, bool expect_case_expression, size_t expected_when_then_size, bool expect_else_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::CaseExpression>(*expression));
+
+        const auto& case_ = static_cast<const SQL::CaseExpression&>(*expression);
+
+        const auto& case_expression = case_.case_expression();
+        EXPECT_EQ(case_expression.is_null(), !expect_case_expression);
+        if (case_expression)
+            EXPECT(!is<SQL::ErrorExpression>(*case_expression));
+
+        const auto& when_then_clauses = case_.when_then_clauses();
+        EXPECT_EQ(when_then_clauses.size(), expected_when_then_size);
+        for (const auto& when_then_clause : when_then_clauses) {
+            EXPECT(!is<SQL::ErrorExpression>(*when_then_clause.when));
+            EXPECT(!is<SQL::ErrorExpression>(*when_then_clause.then));
+        }
+
+        const auto& else_expression = case_.else_expression();
+        EXPECT_EQ(else_expression.is_null(), !expect_else_expression);
+        if (else_expression)
+            EXPECT(!is<SQL::ErrorExpression>(*else_expression));
+    };
+
+    validate("CASE WHEN 16 THEN 17 END", false, 1, false);
+    validate("CASE WHEN 16 THEN 17 WHEN 18 THEN 19 END", false, 2, false);
+    validate("CASE WHEN 16 THEN 17 WHEN 18 THEN 19 ELSE 20 END", false, 2, true);
+
+    validate("CASE 15 WHEN 16 THEN 17 END", true, 1, false);
+    validate("CASE 15 WHEN 16 THEN 17 WHEN 18 THEN 19 END", true, 2, false);
+    validate("CASE 15 WHEN 16 THEN 17 WHEN 18 THEN 19 ELSE 20 END", true, 2, true);
+}
+
+TEST_CASE(collate_expression)
+{
+    EXPECT(parse("COLLATE").is_error());
+    EXPECT(parse("COLLATE name").is_error());
+    EXPECT(parse("15 COLLATE").is_error());
+
+    auto validate = [](StringView sql, StringView expected_collation_name) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::CollateExpression>(*expression));
+
+        const auto& collate = static_cast<const SQL::CollateExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*collate.expression()));
+        EXPECT_EQ(collate.collation_name(), expected_collation_name);
+    };
+
+    validate("15 COLLATE fifteen", "fifteen");
+    validate("(15, 16) COLLATE chain", "chain");
+}
+
+TEST_CASE(is_expression)
+{
+    EXPECT(parse("IS").is_error());
+    EXPECT(parse("IS 1").is_error());
+    EXPECT(parse("1 IS").is_error());
+    EXPECT(parse("IS NOT").is_error());
+    EXPECT(parse("IS NOT 1").is_error());
+    EXPECT(parse("1 IS NOT").is_error());
+
+    auto validate = [](StringView sql, bool expected_invert_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::IsExpression>(*expression));
+
+        const auto& is_ = static_cast<const SQL::IsExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*is_.lhs()));
+        EXPECT(!is<SQL::ErrorExpression>(*is_.rhs()));
+        EXPECT_EQ(is_.invert_expression(), expected_invert_expression);
+    };
+
+    validate("1 IS NULL", false);
+    validate("1 IS NOT NULL", true);
+}
+
+TEST_CASE(match_expression)
+{
+    HashMap<StringView, SQL::MatchOperator> operators {
+        { "LIKE", SQL::MatchOperator::Like },
+        { "GLOB", SQL::MatchOperator::Glob },
+        { "MATCH", SQL::MatchOperator::Match },
+        { "REGEXP", SQL::MatchOperator::Regexp },
+    };
+
+    for (auto op : operators) {
+        EXPECT(parse(op.key).is_error());
+
+        StringBuilder builder;
+        builder.append("1 ");
+        builder.append(op.key);
+        EXPECT(parse(builder.build()).is_error());
+
+        builder.clear();
+        builder.append(op.key);
+        builder.append(" 1");
+        EXPECT(parse(builder.build()).is_error());
+    }
+
+    auto validate = [](StringView sql, SQL::MatchOperator expected_operator, bool expected_invert_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::MatchExpression>(*expression));
+
+        const auto& match = static_cast<const SQL::MatchExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*match.lhs()));
+        EXPECT(!is<SQL::ErrorExpression>(*match.rhs()));
+        EXPECT_EQ(match.type(), expected_operator);
+        EXPECT_EQ(match.invert_expression(), expected_invert_expression);
+    };
+
+    for (auto op : operators) {
+        StringBuilder builder;
+        builder.append("1 ");
+        builder.append(op.key);
+        builder.append(" 1");
+        validate(builder.build(), op.value, false);
+
+        builder.clear();
+        builder.append("1 NOT ");
+        builder.append(op.key);
+        builder.append(" 1");
+        validate(builder.build(), op.value, true);
+    }
+}
+
+TEST_CASE(null_expression)
+{
+    EXPECT(parse("ISNULL").is_error());
+    EXPECT(parse("NOTNULL").is_error());
+    EXPECT(parse("15 NOT").is_error());
+
+    auto validate = [](StringView sql, bool expected_invert_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::NullExpression>(*expression));
+
+        const auto& null = static_cast<const SQL::NullExpression&>(*expression);
+        EXPECT_EQ(null.invert_expression(), expected_invert_expression);
+    };
+
+    validate("15 ISNULL", false);
+    validate("15 NOTNULL", true);
+    validate("15 NOT NULL", true);
+}
+
+TEST_CASE(between_expression)
+{
+    EXPECT(parse("BETWEEN").is_error());
+    EXPECT(parse("NOT BETWEEN").is_error());
+    EXPECT(parse("BETWEEN 10 AND 20").is_error());
+    EXPECT(parse("NOT BETWEEN 10 AND 20").is_error());
+    EXPECT(parse("15 BETWEEN 10").is_error());
+    EXPECT(parse("15 BETWEEN 10 AND").is_error());
+    EXPECT(parse("15 BETWEEN AND 20").is_error());
+    EXPECT(parse("15 BETWEEN 10 OR 20").is_error());
+
+    auto validate = [](StringView sql, bool expected_invert_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::BetweenExpression>(*expression));
+
+        const auto& between = static_cast<const SQL::BetweenExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*between.expression()));
+        EXPECT(!is<SQL::ErrorExpression>(*between.lhs()));
+        EXPECT(!is<SQL::ErrorExpression>(*between.rhs()));
+        EXPECT_EQ(between.invert_expression(), expected_invert_expression);
+    };
+
+    validate("15 BETWEEN 10 AND 20", false);
+    validate("15 NOT BETWEEN 10 AND 20", true);
+}
+
+TEST_CASE(in_table_expression)
+{
+    EXPECT(parse("IN").is_error());
+    EXPECT(parse("IN table").is_error());
+    EXPECT(parse("NOT IN").is_error());
+    EXPECT(parse("NOT IN table").is_error());
+
+    auto validate = [](StringView sql, StringView expected_schema, StringView expected_table, bool expected_invert_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::InTableExpression>(*expression));
+
+        const auto& in = static_cast<const SQL::InTableExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*in.expression()));
+        EXPECT_EQ(in.schema_name(), expected_schema);
+        EXPECT_EQ(in.table_name(), expected_table);
+        EXPECT_EQ(in.invert_expression(), expected_invert_expression);
+    };
+
+    validate("15 IN table", {}, "table", false);
+    validate("15 IN schema.table", "schema", "table", false);
+
+    validate("15 NOT IN table", {}, "table", true);
+    validate("15 NOT IN schema.table", "schema", "table", true);
+}
+
+TEST_CASE(in_chained_expression)
+{
+    EXPECT(parse("IN ()").is_error());
+    EXPECT(parse("NOT IN ()").is_error());
+
+    auto validate = [](StringView sql, size_t expected_chain_size, bool expected_invert_expression) {
+        auto result = parse(sql);
+        EXPECT(!result.is_error());
+
+        auto expression = result.release_value();
+        EXPECT(is<SQL::InChainedExpression>(*expression));
+
+        const auto& in = static_cast<const SQL::InChainedExpression&>(*expression);
+        EXPECT(!is<SQL::ErrorExpression>(*in.expression()));
+        EXPECT_EQ(in.expression_chain()->expressions().size(), expected_chain_size);
+        EXPECT_EQ(in.invert_expression(), expected_invert_expression);
+
+        for (const auto& chained_expression : in.expression_chain()->expressions())
+            EXPECT(!is<SQL::ErrorExpression>(chained_expression));
+    };
+
+    validate("15 IN ()", 0, false);
+    validate("15 IN (15)", 1, false);
+    validate("15 IN (15, 16)", 2, false);
+
+    validate("15 NOT IN ()", 0, true);
+    validate("15 NOT IN (15)", 1, true);
+    validate("15 NOT IN (15, 16)", 2, true);
+}
+
+TEST_MAIN(SqlExpressionParser)