Question

我正在学习mysql，我遇到了一个产生＃1066的表的问题 - 错误不是唯一的表别名。我尝试了许多不同的查询，但都有相同的结果。有人可以让我摆脱痛苦，帮助指出我做错了什么！ - 谢谢

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

我试过的查询 - add_look_item是复合键

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'

由于

Answer 1

为add_look_item创建一个别名，因为您多次加入它。

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该怎么做：）

Answer 2

试试这个 -

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

＃1066 - 错误不是唯一的表别名

2 个答案: