＃1066 - 错误不是唯一表别名

Question

我正在学习mysql，我遇到了一个产生＃1066的表的错误 - 错误不是唯一的表别名。我尝试了许多不同的查询，但都具有相同的结果。有人能让我摆脱苦难，帮助指出我做错了什么！ - 感谢

表

looks 
--------- 

look_id(Pk) 
user_id 
title 
description 
date_modified 

Add_Look_Item 
----------------------- 

look_id (fk from table 1) 
item_id (fk from table 3) 

Item 
-------------- 

item_id (pk) 
name 
details 

Add_Images 
------------------- 
image_id (pk) 
item_id (fk from table 3) 
image_name 

查询我曾尝试 - add_look_item是一个复合键

SELECT DISTINCT looks.look_id, looks.title, looks.date_modified, add_look_item.item_id,  add_images.image_name FROM looks JOIN add_look_item ON add_look_item.look_id = looks.look_id 
JOIN add_look_item ON add_look_item.item_id = item.item_id WHERE look.user_id = 94 

#1066 - error not unique table alias 'add_look_item 

SELECT DISTINCT looks.look_id, looks.title, looks.date_modified, add_look_item.item_id,  add_images.image_name FROM looks JOIN 
add_look_item ON add_look_item.looks_id = look.look_id 
JOIN add_look_item ON add_look_item.item_id = item.item_id 
JOIN add_images ON add_images.item_id = item.item_id WHERE add_look_item.item_id = item.item_id AND look.user_id = 94 

#1066 - error not unique table alias 'add_look_item 

SELECT DISTINCT looks.look_id, looks.title, looks.date_modified, add_look_item.item_id, add_images.image_name FROM looks INNER JOIN add_look_item ON add_look_item.look_id = look_look_id 
INNER JOIN add_images ON add_images.item_id = item.item_id 
INNER JOIN add_look_item ON add_look_item.item_id = item.item_id 
WHERE look.user_id = 94 

#1066 - error not unique table alias 'add_look_item 

SELECT DISTINCT looks.look_id, looks.title, looks.date_modified, add_look_item.item_id, add_images.image_name FROM looks 
INNER JOIN add_look_item ON add_look_item.looks_id = look.look_id 
INNER JOIN add_images ON add_images.item_id = item.item_id 
INNER JOIN add_look_item ON add_look_item.item_id = item.item_id 
WHERE add_look_item.item_id = item.item_id AND look.user_id = 94 


#1066 - error not unique table alias 'add_look_item 

SELECT DISTINCT looks.look_id, looks.title, looks.date_modified, add_look_item.item_id, add_images.image_name FROM looks 
INNER JOIN add_look_item ON add_look_item.looks_id = look.look_id 
INNER JOIN add_images ON add_images.item_id = item.item_id 
WHERE add_look_item.item_id = item.item_id AND look.user_id = 94 

#1054 - Unknown column 'item.item_id' in 'where clause' 

感谢

Answer 1

试试这个是什么 -

SELECT looks.look_id, looks.title, looks.date_modified, add_look_item.item_id, add_images.image_name 
FROM looks 
JOIN add_look_item 
    ON looks.look_id = add_look_item.look_id 
JOIN add_images 
    ON add_look_item.item_id = add_images.item_id 
WHERE look.user_id = 94 

Answer 2

，因为你是多次加入使它的add_look_item的别名。

例如：

SELECT tbl.a, a.y, b.y 
FROM tbl 
JOIN tbl2 as a ON tbl.x = a.x 
JOIN tbl2 as b ON tbl.x = b.x 

否则查询引擎将不知道做:)