Subquery returns more than 1 row 解决方案

通过这个字面意思都能明白，就是子查询的结果不止1条。比如：

select userName,roleId,(case when orgID!='' then (SELECT name FROM organization WHERE orgID=orgID) END) as orgName,
(CASE WHEN bid!='' THEN(SELECT name FROM building WHERE bid=bid) END) AS buildName from user where userName='tj'

执行这句sql时总是报错：-- SELECT name FROM building WHERE bid=1

                                      [Err] 1242 - Subquery returns more than 1 row

但是单独执行"SELECT name FROM building WHERE bid=1"时，确只返回一条记录。百思不得其解！！

后来抱着试试的态度，把building表的bid改成id，

select userName,roleId,(case when orgID!='' then (SELECT name FROM organization WHERE id=orgID) END) as orgName,
(CASE WHEN bid!='' THEN(SELECT name FROM building WHERE id=bid) END) AS buildName from user where userName='tj'

这样就没再报错。为了保险起见，也将organization的主键orgID 改成id。