主表如何統計在附表中的出現次數？

建立主表：

create table a1 (id int ,name char(20));

建立附表:

create table a2 (tid int ,name char(20));

分別插入數據:

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語句：

select a.*,(select count(1) from a2 as b where b.tid=a.id) from a1 as a;

這樣就能查詢a1中所有的id，對應的在a2表中出現了多少次!!

posted on 2014-07-12 22:42?一生學習,何來畢業 閱讀(...) 評論(...) 編輯 收藏

轉載于:https://www.cnblogs.com/shibazi/p/3840542.html

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