查询

SELECT name,age FROM students ORDER BY age:

查询 student表的name，age并且age按降序排列(默认升序)

SELECT name,age FROM students ORDER BY age DESC:

查询 student表的name，age并且age按降序排列

SELECT name,age FROM students ORDER BY age DESC,name:

查询 student表的name，age并且age按降序排列 名字也按升序排列

SELECT name,age FROM students ORDER BY age LIMIT 3;

查询 student表的name，age并且age按降序排列 显示前三个

SELECT name,age FROM students ORDER BY age ASC;

查询 student表的name，age并且age升序序排列

SELECT name,age FROM students WHERE age = 17:

查询 student表的name,age条件是age=17

select name,age from students where age = 18 or age = 19 ;

只有18 19的人

SELECT Name,age from students WHere age not in (18,19);

不在18 19 的 全部返回

select name,age,height from students where (height = 170 or height = 180) and age <= 19 ;

返回170 180 并且年龄 大于等于19

select * from students where height = null ;

返回身高等于null的

select name,age,birthday from students where birthday BETWEEN "1997/6/1" and "1997/12/31";

返回这个日期之间的值

SELECT name,age FROM students where age <> 18;

返回年龄不等于18的

SELECT name,age from students where age != 18

返回年龄不等于18的

= != < > <= =>

等于 不等于 小于 大于 小于等于 大于等于