表 1:tbl_users:
+----+--------+
| id | name |
+----+--------+
| 1 | waheed |
+----+--------+
| 2 | fareed |
+----+--------+
表 2:tbl_watched:
+------------+----+--------+
| id_watched | id | name |
+------------+----+--------+
| 1 | 2 | fareed |
+------------+----+--------+
如果 tbl_watched 不存在，我想获取总记录，它应该返回为 zero 或 null
输出:
+----+--------+--------+
| id | name |watched |
+----+--------+--------+
| 1 | waheed | 90 |
+----+--------+--------+
| 2 | fareed | null |
+----+--------+--------+
我怎样才能得到这样的结果？
最佳答案
使用左连接
Select t1.id , t1.name, count(*) as total from tbl_users as t1
left join tbl_watched as t2 on t1.id=t2.id_watched
group by t1.id , t1.name
关于mysql - 如何从总记录中获取不存在的记录为空？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44154019/