Method parse_set_operator

src/sql-parser/src/parser.rs:7802–7809

(&self, token: &Option<Token>)

    }

    fn parse_set_operator(&self, token: &Option<Token>) -> Option<SetOperator> {
        match token {
            Some(Token::Keyword(UNION)) => Some(SetOperator::Union),
            Some(Token::Keyword(EXCEPT)) => Some(SetOperator::Except),
            Some(Token::Keyword(INTERSECT)) => Some(SetOperator::Intersect),
            _ => None,
        }
    }

    /// Parse a restricted `SELECT` statement (no CTEs / `UNION` / `ORDER BY`),
    /// assuming the initial `SELECT` was already consumed