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

子查询中select count(1) as num from A where A.ID = B.ID 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

Mysql中可以执行,符合mysql规范,默认返回第一条记录的id 但是oracle不能执行,报ORA-00937,所以不符合oracle规范

SELECT SUM ( t.iSum ) as sum FROM ( select count(A.abc) as iSum from A left join B on A.id=B.id where A.abc='1' group by A.abc ); 或者 select count(A.abc) as sum from A left join B on A.id=B.id where A.abc='1'

你这是从一个数据表中查询还是两个数据表中查询啊,因为你给的都是tab1,还有一定要写到一起,是不是有关联,关联在哪个字段上面?你要写清楚,我才知道你想要的SQL语句了

limit 10不能在 order 后面哦

select sum(a)as nums into #temp from table1 where b=3

select怎么写成selcet了,语句的意思是找出A中C=1的a与B中d=1的b相同 select count(*) from (select a from dbo.A where c=1 intersect select b from dbo.B where d=1) as C select distinct count(*) from (select a from dbo.A where c=1 int...

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。

-- 查询所有同学的学号、姓名、选课数、总成绩;select S.Sid,Sname,选课数=COUNT(Cid),总成绩=SUM(Score) from Student S join Sc on S.Sid=sc.Sid group by S.Sid,Sname-- 查询学过“叶萍”老师所教的所有课程的同学学号、姓名;select S.Sid,Sn...

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