从另一个表计数[MySQL的]

Question

我有一台这样的：

+----+---------+-------------+ 
| id | site_id | search_term | 
+----+---------+-------------+ 
| 1 |  2 | apple  | 
| 2 |  2 | banana  | 
| 3 |  3 | cheese  | 
| 4 |  1 | aubergine | 
+----+---------+-------------+ 

而另一个是这样的：

+----+---------+-------------+ 
| id | site_id | search_term | 
+----+---------+-------------+ 
| 1 |  2 |   1 | 
| 2 |  2 |   2 | 
| 3 |  2 |   1 | 
| 4 |  2 |   1 | 
| 5 |  3 |   3 | 
| 6 |  1 |   4 | 
+----+---------+-------------+ 

我想找出每个SEARCH_TERM在多少次显示出来第二张桌子，以及多少次。

换句话说，从这个数据，如果我问SITE_ID 2，我想这将返回：

+-------------+-------+ 
| search_term | count | 
+-------------+-------+ 
| apple  |  3 | 
| banana  |  1 | 
+-------------+-------+ 

我熟悉基本的连接和等，以及COUNT ，但我不知道如何从另一张桌子数数。

谢谢！

Answer 1

试试这个：

select t1.search_term, count(*) from t1 
join t2 on t1.id = t2.search_term and t1.site_id = t2.site_id 
where t1.site_id = 2 
group by t1.search_term 

Answer 2

你可以加入表一起，数排在第二表中的号码：

select t1.search_term 
,  count(t2.id) 
from table1 t1 
left join table2 t2 
on  t1.id = t2.search_term 
group by t1.search_term