Question

我有两个表，一个名为logs，另一个名为location。

在logs中，我有以下内容：

___________________________
| id | message | location |
'-------------------------'
| 1  | test    | 1        |
| 2  | test    | 2        |
| 3  | test    | 1        |
| 4  | test    | 1        |
___________________________

在location表中，我有这个：

_________________
| id | location |
'---------------'
| 1  | US       |
| 2  | UK       |
_________________

我想用我的查询输出的是：

___________________________
| id | message | location |
'-------------------------'
| 1  | test    | US       |
| 2  | test    | UK       |
| 3  | test    | US       |
| 4  | test    | US       |
___________________________

我该怎么做？

Answer 1

试试这个：

select lg.id, lg.message, lo.location 
from logs lg, location lo 
where lg.location = lo.id

Answer 2

SELECT logs.id, logs.message,location.location 
from logs, location 
where logs.location= location.location

在此查询中应用的加入是内连接。

Answer 3

 select a.id,a.message,b.location 
 from 
 logs a , location b 
 where 
 logs.location = location.id;

http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html

Answer 4

使用以下查询。

SELECT a.id, a.message, b.location 
      FROM logs a 
           LEFT JOIN location b 
           ON a.location = b.id;

Answer 5

试试这个

 SELECT lo.id,message,location
 FROM logs lo ,location l
 WHERE lo.location = l.id

如何检索列的相应值？

5 个答案: