Question

I have three tables: adapters, connectors, components
I need to be able to search them all to find a corresponding Part Number (part_num)
The part number is unique so I don’t have to worry about multiple entries.

I use GET to find the part number in the URL, set it to $num, and then do the SELECT

What I’ve found is that I should use UNION, however the three tables have different columns and it gives me an error when trying to do the select. In the example below

Using UNION to find references from other tables

This is my code:

if(isset($_GET['num'])) {
$num = $_GET['num'];

$result = mysql_query("SELECT * FROM connectors WHERE part_num = '$num' UNION SELECT * FROM adapters WHERE part_num = '$num' UNION SELECT * FROM components WHERE part_num = '$num'"); }

Any help would be appreciated, so thanks in advance SO =)

Answer 1

You should probably have a fourth table Parts that identifies to which type table each part_num has been allocated. However, without that, you could still get what you’re after with outer joins (wasteful though):

SELECT * FROM
             connectors
   LEFT JOIN adapters   USING(part_num)
   LEFT JOIN components USING(part_num)
WHERE
   part_num = ?

Note that I have used ? as you really should be using prepared statements: if you don’t know why, or what they are, read about Bobby Tables.