Search for user in 3 different tables that have different columns - php

Question

I'm having a hell of a time with this. I have 3 tables of users. They are in different tables because they have different columns depending on the type of user they are.
Now to log in to the site I'm trying to select the user's email and all the other values that correspond to him. Based on some feedback from other users here I wrote my query like this:
$query = "SELECT id, position_id, first_name, last_name, email ";
$query .= "FROM pims ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1 ";
$query .= "UNION ALL SELECT id, district_id, position_id, first_name, last_name, email ";
$query .= "FROM dms ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1 ";
$query .= "UNION ALL SELECT * ";
$query .= "FROM users ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1";
But I get a "Database query failed" message. The query worked fine when I had only one SELECT statement, so I know it's this query that's not working. Any ideas how to fix it?

Answer 1

Doing union all should have the same number of columns in all queries.
$query = "SELECT id, 'garbage_data' AS district_id, position_id, first_name, last_name, email ";
$query .= "FROM pims ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1 ";
$query .= "UNION ALL ";
$query .= "SELECT id, district_id, position_id, first_name, last_name, email ";
$query .= "FROM dms ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1 ";
$query .= "UNION ALL ";
$query .= "SELECT id, district_id, position_id, first_name, last_name, email ";
$query .= "FROM users ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1";
In case you have a missing column. You can add none existent data like:
'garbage_data' AS district_id
This will show a string garbage_data which is just there to make the column count the same.
It can be anything, It can even be '' AS district_id.

Answer 2

First off the number and type of columns need to be the same in a union query. Second I would suggest you to make a view for that and then use the view for convenience since I don't think this is the only spot you will need such a query.
$query = "SELECT id, '' as district_id, position_id, first_name, last_name, email ";
$query .= "FROM pims ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1 ";
$query .= "UNION ALL SELECT id, district_id, position_id, first_name, last_name, email ";
$query .= "FROM dms ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1 ";
$query .= "UNION ALL SELECT id, district_id, position_id, first_name, last_name, email ";
$query .= "FROM users ";
$query .= "WHERE email = '{$email}' ";
$query .= "AND hashed_password = '{$hashed_password}' ";
$query .= "AND com_code IS NULL ";
$query .= "LIMIT 1";