Update mySQL table based on row=column name

Question

A little background so you understand what I'm trying to do. I am making a page that takes two user input products and checks to see if they are compatible with one another. This is an n+1*n mySQL table because there are n products.

The table looks like

name    a    b    c    d    e
a
b
c
d
e

I already know that every product is compatible with itself, so to save time, is there a query that will automatically fill the table out so that I can get

name    a    b    c    d    e
a       1
b            1
c                 1
d                      1
e                           1

Thanks

I forgot to mention, each product can be compatible with an several other products. The diagonal I'm putting in is just a starting point.

Answer 1

Not a direct answer to your question but I felt I had to mention it...

If possible you should consider changing your design to the following:

compatible_products
product1 product2
a        b
a        c
b        d
etc...

If you insert rows for both (a, b) and (b, a) then your query is simple:

SELECT 1
FROM compatible_products
WHERE product1 = 'a' AND product2 = 'b'

Also, when you add new products you won't have to change your database schema.

Answer 2

Not an answer to your question, but this sounds like a design mistake.

This way, you would have to add a new column to your table for every new product that comes up.

I think the much better way would be normalizing the table into one products and one compatibility table.

Each compatibility relationship between a product and another would be one record.

The compatibility table could look like this:

id   product1    product2    

0    12          34          
1    33          32          
2    54          1           
3    65          328    

Queries would become extremely easy. To find out a relationship, you would have to do a simple

SELECT id FROM compatibility WHERE (product1 = 18 and product2 = 23) 
                                OR (product1 = 23 and product2 = 18)