首页 > 代码库 > 主表如何统计在附表中的出现次数?
主表如何统计在附表中的出现次数?
建立主表:
create table a1 (id int ,name char(20));
建立附表:
create table a2 (tid int ,name char(20));
分别插入数据:
mysql> insert into a1 values (1,‘baidu‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a1 values (2,‘qq‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a1 values (3,‘sina‘);Query OK, 1 row affected (0.02 sec)mysql> insert into a2 values (1,‘000‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (1,‘001‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (1,‘002‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (1,‘003‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (2,‘200‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (2,‘201‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (2,‘202‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (2,‘203‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (2,‘204‘);Query OK, 1 row affected (0.00 sec)mysql> insert into a2 values (2,‘205‘);Query OK, 1 row affected (0.01 sec)mysql> insert into a2 values (3,‘300‘);Query OK, 1 row affected (0.01 sec)
sql语句:
select a.*,(select count(1) from a2 as b where b.tid=a.id) from a1 as a;
这样就能查询a1中所有的id,对应的在a2表中出现了多少次!!
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