Method parse_substring_expr

src/sql-parser/src/parser.rs:1496–1526

Parse calls to substring(), which can take the form: - substring('string', 'int') - substring('string', 'int', 'int') - substring('string' FROM 'int') - substring('string' FROM 'int' FOR 'int') - substring('string' FOR 'int')

(&mut self)

    // - substring('string' FROM 'int' FOR 'int')
    // - substring('string' FOR 'int')
    fn parse_substring_expr(&mut self) -> Result<Expr<Raw>, ParserError> {
        self.expect_token(&Token::LParen)?;
        let mut exprs = vec![self.parse_expr()?];
        if self.parse_keyword(FROM) {
            // 'string' FROM 'int'
            exprs.push(self.parse_expr()?);
            if self.parse_keyword(FOR) {
                // 'string' FROM 'int' FOR 'int'
                exprs.push(self.parse_expr()?);
            }
        } else if self.parse_keyword(FOR) {
            // 'string' FOR 'int'
            exprs.push(Expr::Value(Value::Number(String::from("1"))));
            exprs.push(self.parse_expr()?);
        } else {
            // 'string', 'int'
            // or
            // 'string', 'int', 'int'
            self.expect_token(&Token::Comma)?;
            exprs.extend(self.parse_comma_separated(Parser::parse_expr)?);
        }

        self.expect_token(&Token::RParen)?;
        Ok(Expr::Function(Function {
            name: RawItemName::Name(UnresolvedItemName::unqualified(ident!("substring"))),
            args: FunctionArgs::args(exprs),
            filter: None,
            over: None,
            distinct: false,
        }))
    }

    /// Parse an operator reference.
    ///