Select data from multiple tables in same query

Question

I am trying to pull all categories for a blog post when the blog is loaded. I have 2 tables for categories, one for the categories themselves and another that lists which categories are assigned to which blog post.

the MySQL command I have is

SELECT `category_name`, `category_slug` FROM `blog_categories`, `blog_post_categories` WHERE `blog_categories.category_id` = `blog_post_categories.category_id` AND `blog_post_categories.post_id` = 1

But I keep getting the following error

Unknown column 'blog_categories.category_id' in 'where clause'

The two tables are as such:

blog_categories has columns category_id, category_name and category_slug blog_post_categories has columns id, post_id and category_id

Do not use comma-join syntax. And you shouldn't need backticks on properly qualified columns (such as these are) — Strawberry
– Strawberry, Commented Apr 21, 2014 at 15:20

Abhik Chakraborty · Accepted Answer · 2014-04-21 15:09:22Z

3

Your backticts are not in proper place should be as

SELECT `category_name`, 
`category_slug` 
FROM 
`blog_categories`, `blog_post_categories` 
WHERE `blog_categories`.`category_id` = `blog_post_categories`.`category_id` 
AND `blog_post_categories`.`post_id` = 1

answered Apr 21, 2014 at 15:09

Abhik Chakraborty

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1 Comment

Mark Railton Over a year ago

Abhik, thank you so much. Still a noob with sql so this helps alot. Will accept as soon as am able to.

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