MySQL Table Analysis

I am conducting a detailed analysis across multiple MySQL tables. Here's a summarized look at what I'm trying to accomplish:

Summary:

Table one contains item_number1 and item_number2. I need to compare each of the item_numbers in table one to 20+ other MySQL tables. Here's the catch; I do not know which columns to search in the 20+ other tables.

Desired Output:

• Item1 = 123456 is found in table2 X number of times
• Item2 = 789101 is found in table2 X number of times

What I've tried:

• GREP - By grepping for each item_number over all MySQL .MYD files I can identify matches. This doesn't seem practical to start 100+ million times.
• MySQL - Creating a parallel loop to run multiple queries simultaneously. Again, this doesn't seem practical.

I'm assuming there's a way to accomplish this using some sort of open source ETL tool, but I haven't had any success in my searches to-date. Any input or guidance would be greatly appreciated.