MySQL-LEFT JOIN无法正常工作

Question

I have 2 tables.

attribute
=========
ID  Name
-------------------
1   Size
2   Colour


product_attribute
=========
ID  attribute_id
-------------------
1   1

I want to show any values contained in the attribute table that are missing from the product_attribute table.

This code results in "size" when I expected "colour". What am I missing?

SELECT name FROM attribute a LEFT JOIN product_attribute p ON a.id = p.attribute_id

Answer 1

SELECT a.name FROM attribute a 
LEFT JOIN product_attribute p ON a.id = p.attribute_id
where p.attribute_id is null

Answer 2

您可以改用：

SELECT name FROM attribute where ID  not in (select attribute_id from product_attribute)