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SQL语句理解 sElECt * From B whErE (sElECt Count...

select count(*) from aa where (select * from aa where a=1)错了 select count(*) from aa where a=1 select count(*) from aa where a in (select a from aa where a=1)

就是统计B表和A表用ID连接的行数,子查询的行数=0,就可以实现从B表中排除A表数据。 一、SQL语句简介:SQL 全名是结构化查询语言(Structured Query Language),是用于数据库中的标准数据查询语言,IBM 公司最早使用在其开发的数据库系统中。19...

因为你定义了字段名是num,就是as某某就是将得到结果放到字段NUM中

sql="select count(*) from Cui where Time like '%2011%'"; 这样就可以了 楼主看下 like的用法吧

SELECT + COUNT(编号) + FROM + 职工表 + WHERE + YEAR(NOW())- + YEAR(进厂日期) + >=25 获取 编号的数量 来自于 职工表 条件是 当前年分-进厂日期 >= 25 【工龄>= 25 的职工数量】

select a. col1, b.col2 from (select count(id) as col1 from table1) as a, (select count(id) as col2 from table2) as b -------------这样写。

select systemdate from B语句取出的结果不止一个吧?这样写不行的。除非只有一个: select top 1systemdate from B。

limit 10不能在 order 后面哦

Select A, count(B) as total, sum(case when B > 30 then 1 else 0 end) as total1, sum(case when B > 20 then 1 else 0 end) as total2 from ABC group by A

--into #a,这是生成新表与查询结果不可以分在同一个语句里 select count(*) from rszl --如果是结果集 select count(*) from (select * from rszl) as t 或 select count(*) from ..........

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