如何用SQL语句查询Table表中的ID1中的O1，O2，O3为1 的数目
问题描述：
如何用SQL语句查询Table表中的ID1中的O1，O2，O3为1 的数目
Table
ID O1 O2 O3
ID1 1 1 0
ID2 1 0 1
ID3 0 1 1
答
select COUNT(*), (select COUNT(*) FROM a where O1='1') AS COUNTO1,(SELECT COUNT(*) FROM A WHERE O2="1") AS COUNTO2 ,(SELECT COUNT(*) FROM A WHERE O3="1") AS COUNT03 FROM A
答
select count(*) from table where O1='1';难道不是这个？
答
select COUNT(*), (select COUNT(*) FROM a where O1='1') AS COUNTO1,(SELECT COUNT(*) FROM A WHERE O2="1") AS COUNTO2 ,(SELECT COUNT(*) FROM A WHERE O3="1") AS COUNT03 FROM A
答
来个不一样的：
select count(case when O1 = '1' then 1 end) count01,
count(case when O2 = '1' then 1 end) count02,
count(case when O3 = '1' then 1 end) count03
from A