一条简单的SQL语句，请各位大侠帮忙呀～

[米奇露]

假设有一个表：TABAL TONGJI
字段：ID
KHID(客户ID)
SL（数量）
DJ (单价)
FLAG（标志标准收费和实际收费，分别为0和1）
请问要怎样写一条SQL语句，统计标准收费的SUM(SL*DJ)减去实际收费的SUM(SL*DJ),GROUP BY KHID?

[lidengdeng]

sql1="SELECT KHID, SUM(SL*DJ) AS BZ WHERE FLAG=0 GROUP BY KHID"
sql2="SELECT KHID, SUM(SL*DJ) AS SJ WHERE FLAG=1 GROUP BY KHID"
sql="SELECT a.KHID,a.BZ-b.SJ AS diff FROM (" + sql1 + ") a, (" + sql2 + ") b WHERE a.KHID=b.KHID "

[tenlicmatthew]

try:
select KHID,(sum(dj*sl*decode(flag,0,1,0)) - sum(dj*sl*decode(flag,1,1,0))) yourresult from tongji group by khid

不过效率有多高你自己看了

[米奇露]

哎呀，真的行了呀，还可以用这种方式呀：FROM (" + sql1 + ") a, (" + sql2 + ") b，一条SQL语句像表一样使用吗？不过还有点问题，sql1和sql2选出来得记录数不一定一样多，是不是还有用外连接的方式吗？