where the comparison operation
> < >= = <= != (select * from students where age = 18)
The logical operation where
and or not (select *from student where age = 18 and ( or ) gender = "女")
not use cases (look for students less than 18 years, female gender and select * from students where not age> 18 and gender = "female")
where the fuzzy query
1. like
2%: to represent any number of any character
3. _: represents an arbitrary character (e.g.: select * from students where name = "Small%" [% smaller,%% small, small _, __ small, __%])
Where the scope of a query (query into a range of continuous and discontinuous range query range queries)
in : 非连续 select name from students where age in (18,34);
between ... and ... : select name from students where age between 18 and 34;
where the null value is determined
is null: Analyzing represents null value (select * from students where age is null)
It is not null: determination indicates a non-null value (select * from students where age is not null)