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

你既然想用COUNT进行统计,那么就要有分组啊,不分组统计的数据有什么意义呢?建议加上GROUP BY语句吧!

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

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

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

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

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 count(id) from student where name='"+传进来的值+"'";

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。

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'

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