Question

我正在进行数据库连接，我想执行以下操作：

Select tabel_one.id, 
       tabel_one.title, 
       tabel_one.content, 
       table_two.value as table_two.key 
  from tabel_one 
  Join table_two ON table_two.id = table_one.id ....

重要的部分是：

table_two.value as table_two.key

有没有办法可行？

Answer 1

不，您无法定义引用表的别名。

一般情况下，您应该使用：

table_two.value as key

否则，作为OMG Ponies suggested in another answer，您可以在反引号中包装别名：

table_two.value as `table_two.key`

Answer 2

此：

Select tabel_one.id, 
       tabel_one.title, 
       tabel_one.content, 
       table_two.value as `table_two.key` 
  from tabel_one 
  Join table_two ON table_two.id = table_one.id

...适用于MySQL 5.1.35。由于这段时间，你需要用反引号括起别名

Answer 3

根据您的comment on this answer判断，我希望您真正想要的是：

Select tabel_one.id,  
       tabel_one.title,  
       tabel_one.content,  
       table_two.value as tags,
       table_three.value as author
  from table_one  
  LEFT Join table_two ON table_two.id = table_one.id 
  AND table_two.key= 'tags'
  LEFT Join table_three ON table_three.id = table_one.id 
  AND table_three.key= 'author'

SQL选择table1.column作为表1.column

3 个答案: