SqlServer 基础知识 数据检索、查询排序语句

复制代码 代码如下:
--执行顺序 From Where Select
select * from
(select sal as salary,comm as commission from emp ) x where salary<5000
--得出 Name Work as a Job
select ename +' Work as a'+job as msg from emp where deptno=10
--如果员工工资小于2000返回UnderPaid 大于等于4k 返回OverPaid 之间返回OK
select ename,sal,
case when sal<2000 then 'UnderPaid'
when sal>=4000 then 'OverPaid'
else
'OK'
end
from emp
--从表中随机返回N条记录 newid()
--order by 字句中指定数字常量时，是要求根据select列表中相应位置的列排序
--order by 字句中用函数时，则按函数在没一行计算结果排序
select top 5 ename from emp order by newid()
--找空值is null
select * from emp where comm is null
--将空值转换为实际值
--解释：返回其参数中第一个非空表达式
--coalesce 联合，合并，结合.英音：[,k"" src="/UploadFiles/2021-04-09/20111025145933625.png">