Question

I have 2 tables: files and user.

files
----------------------------
|Fileid  | name  | type    |
----------------------------
| 01     | file1 | private |
| 02     | file2 | private |
| 03     | file3 | Public  |
----------------------------

and

user
---------------------
| Fileid  | UserId  |
---------------------
| 01      | user1   | 
| 02      | user1   |
---------------------

How would I select all the record(private and public) for who ever id is in the ‘user’ table and only ‘public’ files for any other user where the ‘userid’ is not in the ‘user’ table? please help

Answer 1

If I correctly understand the problem, you are looking for a LEFT JOIN favoring files returning all fields for non-null UserId, or Public only when UserId IS NULL.

SELECT 
  files.*
FROM files LEFT JOIN user ON files.Fileid = user.Fileid
WHERE 
  user.UserId IS NOT NULL
  OR (user.UserId IS NULL AND files.type = 'Public')