MySQL SUM() 带条件的求和方法与多条件的求和方法

一、单一的求和。

select sum(value) as value from table where user_id = 1 and type = 6 and type_son = 2

value 为求和的字段。

as 后面是 sum 求和后给它一个名称。

二、SQL语句中嵌套语句多条件求和。

select 

(select sum(value) from table where type = 6 and type_son = 1) as xj0,

(select sum(value) from table where type = 6 and type_son = 2) as xj1,

(select sum(value) from table where type = 3 and type_son = 3) as xj2,

(select sum(value) from table where type = 4 and type_son = 3) as xj3

from table where user_id = 1 limit 0,1

as 后面是 sum 求和后给它一个名称，这样就不会冲突。

三、与第二个一样，但是不采取语句嵌套的方式求和，而是使用 sum 判断求和。

select 

sum(IF(type = 6 and type_son = 1,value,NULL)) as xj0,

sum(IF(type = 6 and type_son = 2,value,NULL)) as xj1,

sum(IF(type = 3 and type_son = 0,value,NULL)) as xj2,

sum(IF(type = 4 and type_son = 3,value,NULL)) as xj3

from table where user_id = 1

sum(IF('条件判断'，'求和的字段'，'NULL不计算'))  as  '别名'

我觉得第三个的方式比前面两个的方式要好。

YII 2.0 使用 SUM 求和

$v['alls_bonus'] = AccountingLog::find()
        ->select(["
            sum( IF(type = 6 and type_son = 1,value,NULL) ) as xj0,
            sum( IF(type = 6 and type_son = 4,value,NULL) ) as xj1,
            sum( IF(type = 8 and type_son = 4,value,NULL) ) as xj2, 
            sum( IF(type = 3 and type_son = 1,value,NULL) ) as xj3
        "])
        ->where(['user_id'=>1])
        ->asArray()
        ->one();

注意要在 select 里面加 ["sum........"]，否则会报错