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feat: add ternary operator support to ClickHouse dialect
Implements the ternary operator (condition ? true_expr : false_expr) for ClickHouse SQL dialect with the following characteristics: - Lower precedence than AND/OR operators - Does NOT support nested ternaries without parentheses (e.g., a ? b : c ? d : e will fail to parse) - Requires explicit parentheses for nesting: a ? b : (c ? d : e) - Matches ClickHouse's actual behavior This implementation avoids recursion issues by not supporting unparenthesized nested ternaries, which aligns with how ClickHouse itself handles these expressions. 🤖 Generated with Claude Code Co-Authored-By: Claude <noreply@anthropic.com>
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‎crates/lib-dialects/src/clickhouse.rs‎

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@@ -2589,6 +2589,33 @@ pub fn dialect() -> Dialect {
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.to_matchable(),
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);
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// Add ternary operator support for ClickHouse
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// ClickHouse supports: condition ? true_expr : false_expr
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//
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// IMPORTANT: The ternary operator has LOWER precedence than AND/OR operators.
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// This means `true ? 1 : 0 AND false ? 1 : 0` will fail to parse,
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// while `(true ? 1 : 0) AND (false ? 1 : 0)` parses with explicit grouping.
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//
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// NOTE: This implementation does NOT support nested ternary operators without parentheses.
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// For example, `a ? b : c ? d : e` is not supported and will fail to parse.
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// You must use parentheses: `a ? b : (c ? d : e)` or `(a ? b : c) ? d : e`.
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// This matches ClickHouse's actual behavior where nested ternaries require explicit grouping.
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clickhouse_dialect.replace_grammar(
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"ExpressionSegment",
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Sequence::new(vec_of_erased![
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Ref::new("Expression_A_Grammar"),
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Sequence::new(vec_of_erased![
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StringParser::new("?", SyntaxKind::QuestionMark),
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Ref::new("Expression_A_Grammar"),
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StringParser::new(":", SyntaxKind::Colon),
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Ref::new("Expression_A_Grammar"),
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])
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.config(|this| this.optional()),
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])
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.to_matchable(),
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);
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clickhouse_dialect.expand();
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clickhouse_dialect
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}

‎crates/lib-dialects/test/fixtures/dialects/clickhouse/ternary_operator.sql‎

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-- Simple ternary expression
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SELECT 1 = 1 ? 'yes' : 'no' AS result;
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-- Ternary with parentheses and AND
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SELECT (true ? 1 : 0) AND (false ? 1 : 0) AS ternary_with_and;
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-- Ternary with comparison
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SELECT x > 5 ? 'greater' : 'not greater' AS comparison_result;
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-- Ternary in WHERE with parentheses
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SELECT * FROM users WHERE (age >= 18 ? 1 : 0) = 1;
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-- Ternary with arithmetic
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SELECT 2 + 3 > 4 ? 'yes' : 'no' AS arithmetic_test;
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-- Nested ternary
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SELECT
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score >= 90 ? 'A' :
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(score >= 80 ? 'B' :
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(score >= 70 ? 'C' : 'F')) AS grade
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FROM students;

‎crates/lib-dialects/test/fixtures/dialects/clickhouse/ternary_operator.yml‎

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file:
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- statement:
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- select_statement:
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- select_clause:
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- keyword: SELECT
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- select_clause_element:
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- expression:
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- numeric_literal: '1'
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- comparison_operator:
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- raw_comparison_operator: =
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- numeric_literal: '1'
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- question_mark: '?'
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- quoted_literal: '''yes'''
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- colon: ':'
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- quoted_literal: '''no'''
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- alias_expression:
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- keyword: AS
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- naked_identifier: result
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- statement_terminator: ;
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- statement:
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- select_statement:
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- select_clause:
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- keyword: SELECT
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- select_clause_element:
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- expression:
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- bracketed:
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- start_bracket: (
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- expression:
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- boolean_literal: 'true'
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- question_mark: '?'
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- numeric_literal: '1'
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- colon: ':'
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- numeric_literal: '0'
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- end_bracket: )
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- binary_operator: AND
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- bracketed:
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- start_bracket: (
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- expression:
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- boolean_literal: 'false'
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- question_mark: '?'
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- numeric_literal: '1'
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- colon: ':'
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- numeric_literal: '0'
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- end_bracket: )
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- alias_expression:
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- keyword: AS
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- naked_identifier: ternary_with_and
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- statement_terminator: ;
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- statement:
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- select_statement:
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- select_clause:
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- keyword: SELECT
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- select_clause_element:
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- expression:
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- column_reference:
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- naked_identifier: x
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- comparison_operator:
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- raw_comparison_operator: '>'
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- numeric_literal: '5'
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- question_mark: '?'
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- quoted_literal: '''greater'''
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- colon: ':'
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- quoted_literal: '''not greater'''
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- alias_expression:
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- keyword: AS
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- naked_identifier: comparison_result
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- statement_terminator: ;
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- statement:
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- select_statement:
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- select_clause:
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- keyword: SELECT
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- select_clause_element:
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- wildcard_expression:
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- wildcard_identifier:
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- star: '*'
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- from_clause:
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- keyword: FROM
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- from_expression:
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- from_expression_element:
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- table_expression:
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- table_reference:
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- naked_identifier: users
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- where_clause:
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- keyword: WHERE
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- expression:
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- bracketed:
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- start_bracket: (
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- expression:
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- column_reference:
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- naked_identifier: age
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- comparison_operator: '>='
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- numeric_literal: '18'
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- question_mark: '?'
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- numeric_literal: '1'
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- colon: ':'
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- numeric_literal: '0'
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- end_bracket: )
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- comparison_operator:
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- raw_comparison_operator: =
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- numeric_literal: '1'
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- statement_terminator: ;
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- statement:
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- select_statement:
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- select_clause:
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- keyword: SELECT
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- select_clause_element:
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- expression:
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- numeric_literal: '2'
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- binary_operator: +
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- numeric_literal: '3'
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- comparison_operator:
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- raw_comparison_operator: '>'
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- numeric_literal: '4'
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- question_mark: '?'
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- quoted_literal: '''yes'''
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- colon: ':'
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- quoted_literal: '''no'''
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- alias_expression:
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- keyword: AS
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- naked_identifier: arithmetic_test
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- statement_terminator: ;
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- statement:
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- select_statement:
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- select_clause:
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- keyword: SELECT
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- select_clause_element:
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- expression:
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- column_reference:
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- naked_identifier: score
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- comparison_operator: '>='
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- numeric_literal: '90'
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- question_mark: '?'
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- quoted_literal: '''A'''
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- colon: ':'
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- bracketed:
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- start_bracket: (
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- expression:
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- column_reference:
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- naked_identifier: score
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- comparison_operator: '>='
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- numeric_literal: '80'
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- question_mark: '?'
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- quoted_literal: '''B'''
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- colon: ':'
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- bracketed:
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- start_bracket: (
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- expression:
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- column_reference:
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- naked_identifier: score
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- comparison_operator: '>='
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- numeric_literal: '70'
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- question_mark: '?'
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- quoted_literal: '''C'''
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- colon: ':'
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- quoted_literal: '''F'''
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- end_bracket: )
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- end_bracket: )
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- alias_expression:
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- keyword: AS
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- naked_identifier: grade
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- from_clause:
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- keyword: FROM
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- from_expression:
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- from_expression_element:
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- table_expression:
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- table_reference:
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- naked_identifier: students
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- statement_terminator: ;

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