Question

I hate to submit a new question, but everyone else has some slight thing that is different enough to make this one seem necessary to ask.

Users are to type in a vendor name, and then see all the “kinds” of things they have bought from that company, in a list, sorted by the lowest-inventory-on-hand.

Summary:
I have three tables.
There are more fields than these, but these are the relevant ones (as far as I can tell).

stuff_table
stuff_vendor_name *(search this field with $user_input, but only one result per lookup_type)*
lookup_type

lookup_table
lookup_type
lookup_quantity (order by this)
category_type

category_table
category_type
category_location (check if this field == $this_location, which is already assigned)

Wordier Explanation:
The users are searching for a value that is contained only in the stuff_table — distinct stuff_vendor_name values for each lookup_type. Each item can be bought from multiple sources, the idea is to see if any vendor has ever sold even one of any type of item before.

But the results need to be ORDER BY the lookup_quantity, in the lookup_table.

And importantly, I have to check to see if they are searching the correct location for these categories, located in the category_table in the category_location field.

How do I efficiently make this query?
Above, I mentioned the variables that I have:
$user_input (the value we are searching for distinct matches in the stuff_vendor_name field) and $current_location.

To understand the relationship of these tables, I will use an example.
The stuff_table would have dozens of entries with dozens of vendors, but have a lookup_type of, say, “watermelon,” “apple,” or “cherry.”
The lookup_table would give the category_type of “Jellybean.” One category type can have multiple lookup_types. But each lookup_type has exactly one category_type.

Answer 1

I made a nested query instead.

The final code looks like this:

$query_row=mysql_query(
"SELECT DISTINCT * FROM table_a WHERE 
field_1 IN (SELECT field_1 FROM table_b WHERE field_2 = $field_2) 
AND field_3 IN (SELECT field_3 FROM table_c WHERE field_4 = $field_4)
ORDER BY field_5 DESC
");

This was incredibly simple. I just didn’t know you could do a nested query like that.

I read it was “bad form” because it makes some kind of search optimization not as good as it could be, so be careful using nested select statements.

However for me, it seemed to actually be significantly faster.