where the column select lines connected to join
- Operator Precedence
- () The highest priority
- Arithmetic operators: + - * /
- Logical operators: not, and, all
- Comparison Operators
- Comparative single line: =,>,> =, <, <=, <>
- 多行比较:>any,>all,<any,<all,in,not in
- Fuzzy comparison: like (with '%' and '_')
- Special comparison: is null
- Create a table