关于sql 语句的优化！谢谢各位大侠！

[dragon514]

SELECT COUNT(DISTINCT field1) FROM tablename WHERE (field1 IN (SELECT field1 FROM tablename GROUP BY field1 HAVING (SUM(field2) <> 0) OR (SUM(field3) <> 0) OR (SUM(field4) <> 0))

这是小弟写得sql语句.表tablename,字段field1,field2,field3,field4
field1相同的记录可能有多条，我要统计这个表中distinct（field1）的数量，
条件为SUM(field2) <> 0) OR (SUM(field3) <> 0) OR (SUM(field4) <> 0)

[shuiniu]

select count(*) from
(
SELECT field1
FROM tablename
GROUP BY field1
HAVING (SUM(field2) <> 0) OR (SUM(field3) <> 0) OR (SUM(field4) <> 0)
) a

[zjcxc]

SELECT count(*)
FROM tablename
group by field1
having sum(field2)<>0 OR SUM(field3) <> 0 OR SUM(field4) <> 0

[zjcxc]

--上面不对,要这样:

select count(*) from(
SELECT field1
FROM tablename
group by field1
having sum(field2)<>0 OR SUM(field3) <> 0 OR SUM(field4) <> 0
)a

[azsoft]

select count(field1)
from (
SELECT field1
FROM tablename
group by field1
having sum(field2)<>0 OR SUM(field3) <> 0 OR SUM(field4) <> 0
)a