一个单表统计问题

[Soulic]

有表user_log

id   user_id       flag         amount
1    1             1            12000.00
2    1             0            1000.00
3    1             0            560.00
4    1             0            2339.00
5    1             1            798.00
6    1             0            1580.00

flag: 1: 收入 0: 支出

如何写SQL语句查询得到

user_id      收入         支出         总计
1            19980.00     5497.00     25459.00

[ACMAIN_CHM]

select user_id,
sum(flag*amount) as 收入,sum((1-flag)*amount) as 支出,sum(amount) as 总计
from user_log

[feng00~]

SELECT user_id, SUM(CASE flag WHEN 1 THEN amount ELSE 0 END) 收入 , SUM(CASE flag WHEN 0 THEN amount ELSE 0 END) 支出 , SUM(amount) 总金额 FROM user_log GROUP BY user_id