这句话我还是看不懂,select count(1) from T_Late where T_Late.Uid = T_W

来源：学生作业帮编辑：拍题作业网作业帮分类：数学作业时间：2024/04/28 01:16:15

这句话我还是看不懂,
select count(1) from T_Late where T_Late.Uid = T_Worker.Uid and datediff(m,latetime,Getdate()) = 1

datediff是查询两个日期之间相距的函数,第一个参数为m,表示查询的是两个日期相差多少月.
算法就是第三个参数日期减去第二个参数日期.所以 datediff(m,latetime,Getdate()) = 1的意思就是字段latetime距离getdate()(当天)的有多少个月.这个就是从两个月份区分的了.比如今天是5月1日,而latetime是4月30日23点59分59秒,那么返回值也是1,即相差一个月.
前边的count(1)等同于count(*),就是查询符合条件的数据行数.
这么说能明白么?

这句话我还是看不懂,select count(1) from T_Late where T_Late.Uid = T_W select uid from T_TABLE Where num='3' and time between like SQL >select count(*) from Teacher where teacherCode=? and te select count(*) as total from ddcm_news where key=a SQL语句理解 select * from B where (select count(1) as num from A SELECT COUNT(*) FROM Users WHERE Id={0} AND LoginPwd = '{1}' 这个能合并成一句吗?select count(ITEMKIND) from ITEM where ITEMKIND='1 select count(1) from emp select count(distinct b) from X_info where c=1;能放到一个CASE内么不 select * from book where 1=1 select A,B,C,D=(select count(*) from 表 where c=a.a and b=a.b select count(*) from v$process a,v$session b where a.addr =