mysql sum求和的方法：1、通过“select sum(value) as value from table where user_id”方式实现单一求和；2、通过嵌套语句多条件求和，语法如“(select sum(value) from table where type = 6 and type_son = 1) as xj0”。
本教程操作环境：Windows10系统、MySQL5.7版本、Dell G3电脑。
mysql sum求和使用方法是什么？
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
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