Mapper对于数据求和返回值为null怎么解决

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/shichuwu/article/details/81609633

在对于数据求和时返回值为null , 报如下错误:

数据库语句如下:

 SELECT
 FROM
 user
 WHERE
 user_id =#{userid} and YEARWEEK(date_format(create_time,'%Y-%m-%d')) = YEARWEEK(now())-1 and is_delete!='1'

报错原因:数据库中没有符合该条件记录 , 求和没有结果

解决方法:在数据库语句中加个Case语句 

        SELECT
        CASE
        WHEN
        SUM(integral) is null Then 0
        ELSE SUM(integral)
        END
        FROM
        user
        WHERE
        user_id =#{userid} and YEARWEEK(date_format(create_time,'%Y-%m-%d')) = YEARWEEK(now())-1 and is_delete!='1'