oracle sql groupby后 无记录 怎么使count()=0
SELECT A.ab,B.bc,count(1)
FROM A,B
WHERE A.id=B.id
GROUP BY A.ab,B.bc;
因为B表里没有和A表相对应的id,所以查询结果没有记录，
但想在没有记录的时候使count(1)=0怎么写？
SELECT count(1)
FROM A,B
WHERE A.id=B.id
GROUP BY A.ab,B.bc;
这样是可以得到count(1)=0，但我也想当A.id=B.id的时候，取得字段A.ab的值，所以。。。
[最优解释]
','
[其他解释]

SELECT A.ab,B.bc,count(1)
FROM A,B
WHERE A.id=B.id(+)
GROUP BY A.ab,B.bc;

[其他解释]
上面count有误

SELECT 
A.ab,
B.bc,
count(B.id)
FROM A,B
WHERE A.id=B.id(+)
GROUP BY A.ab,B.bc;

[其他解释]
SELECT A.ab,B.bc,count(1)
FROM A,B
WHERE A.id=B.id
GROUP BY A.ab,B.bc;

没有记录就直接为空，有什么问题？？？

显示0的话，则去掉AB字段即可

SELECT count(1)
FROM A,B
WHERE A.id=B.id
GROUP BY A.ab,B.bc;
[其他解释]
楼上
select count(1)
from
(
SELECT A.ab,B.bc
FROM A,B
WHERE A.id=B.id
) C
GROUP BY A.ab,B.bc
当虚拟表C没有记录，怎样使count(1)=0？
[其他解释]
楼上
select case when count(1)=0 then C.ab
when count(1)>0 then C.bc
else 'xxx' end
from
(
SELECT A.ab,B.bc
FROM A,B
WHERE A.id=B.id
) C
GROUP BY A.ab,B.bc
当虚拟表C没有记录，怎样使count(1)=0？
[其他解释]
楼上
select case when count(1)=0 then C.ab
when count(1)>0 then C.bc
else 'xxx' end
from
(
SELECT A.ab,B.bc
FROM A,B
WHERE A.id=B.id
UNION ALL
SELECT NULL,NULL
FROM DUAL
) C
GROUP BY A.ab,B.bc
这样也可以实现效果
[其他解释]
SELECT DECODE(COUNT(*),0,COUNT(*),A.ab