关与DB2数据库将多个count语句合为一个。

Question

select count(*) from db1 where grade = 0;
select count(*) from db1 where grade = 1;
select count(*) from db1 where grade = 2;
select count(*) from db1 where grade = 3;

 

以上4条sql，合成一条可以实现吗？

 

为什么在mysql中可以这样实现：

SELECT (SELECT COUNT(*) FROM db1 WHERE gread = 1) AS g1,(SELECT COUNT(*) FROM db1WHERE gread = 2) AS g2;

 

而DB2中不可以。。。

 

Answer 1

select grade,count(*) from db1 where grade = 0 or grade = 1 or grade = 2 or grade = 3 group by grade;