Question

I have the following 2 tables.

tb_Posts
--------
PostId, PostName

tb_PostCategories
------------------
PostId, PostCategoryName

I want to join both these tables, however, I would like to display all columns and entries in tb_Posts but display PostCategoryName column only from tb_PostCategories even if an entry for tb_Posts.PostId in tb_PostCategories exists or not.

So, I did this query, but it I am getting a SQL error

SELECT *
FROM
(SELECT a.PostId, a.PostName from tb_Posts a) y
LEFT JOIN tb_PostCategories z USING (y.PostId)

Thanks

Answer 1

* gets all columns.
You can do:

SELECT y.*, z.PostCategoryName
  FROM (SELECT a.PostId, a.PostName FROM tb_Posts a) y
       LEFT JOIN tb_PostCategories z 
       ON y.PostId = z.PostId;

---

This doesn’t really seem to require a subquery, however, so to simplify a bit:

SELECT posts.*, cat.PostCategoryName
  FROM tb_Posts posts
       LEFT JOIN tb_PostCategories cat
       ON cat.PostId = posts.PostId;