:排序查询引入: select * from employees; 语法: select_查询列表 from表 where[筛选条件] order by排序列表asc(升序） | desc（降序）不写默认升序 */#1.查询员工信息，要求工资从高到底
SELECT *FROM employees ORDER BY salary DESC;
SELECT *FROM employees ORDER
1.小表驱动大表即小的数据集驱动大的数据集select * from A where id in(where id from B)等价于：select id from B
select * from A where A.id=B.id当B表的数据集小于A表的数据集时，用 in 优于existsselect * from A where exists(select 1 from B w
