mysql中统计特定行问题

[damonxx]

例如表A 有列t_id s_id ct_1 ct_2
数据如下
t_id s_id ct_1 ct_2
a a1 1000 800
a a2 100 100
a a3 50 50

对此表做统计，当 s_id='a2' 时，ct_1字段不计，但ct_2字段要统计，期望得到如下的结果
t_id s_id ct_1 ct_2
a a1 1000 800
a a2 100 100
a a3 50 50
a 合计 1050 950

求查询语句该怎么写？
用sum if(s_id='a2',0,ct_1)、group by with rollup等语句的话，得到的a2所在行的ct_1字段也为0了

[zjcxc]

drop temporary table if exists A;
create temporary table A(t_id varchar(10), s_id varchar(10), ct_1 int, ct_2 int);
insert A values
('a', 'a1', 1000, 800),
('a', 'a2', 100, 100),
('a', 'a3', 50, 50);
select t_id, s_id, sum(if(s_id='a2',0,ct_1)), sum(ct_2)
from a group by t_id, s_id with rollup

没发现问题 +------+------+---------------------------+-----------+ | t_id | s_id | sum(if(s_id='a2',0,ct_1)) | sum(ct_2) | +------+------+---------------------------+-----------+ | a | a1 | 1000 | 800 | | a | a2 | 0 | 100 | | a | a3 | 50 | 50 | | a | NULL | 1050 | 950 | | NULL | NULL | 1050 | 950 | +------+------+---------------------------+-----------+ 5 rows in set (0.00 sec)

[zjcxc]

如果你只是在汇总中不包含  s_id='a2' , 那么应该单独处理汇总

select * from A union all select null, null, sum(if(s_id='a2',0,ct_1)), sum(ct_2) from A