>I have a column that is defined as a SET. For simplicity's sake,
>let's say the column is defined as:
>
>set_col SET ('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', .... 'Z')
>
>After entering a few hundred rows, I know that some but not all
>values of the SET have been used at least once. How can one work
>out which values have been used at least once ?
>
>Doing a SELECT DISTINCT(set_col) on the table might provide
>something like this:
>
>A,B,D
>A,C,G,N,M,P
>C,E,F,H,I,R,S
>C,E,G,I
>D,F
>G,H,L,M,O
>etc
>
>But it then requires processing to work out which
>values have been used at least once. It's not very
>scalable.
>
>Is there a method to retrieve a list of all the values
>that have been used at least once ?
Sir, the basic problem is that you've violated first normal form,
which states columns should only contain atomic (indivisible) data.
Since you plan to divide up the data in your columns, it's obviously
not indivisible.
My recommendation is to brush up on the first three normal forms and
redesign your tables. There may be a way to do what you want with
MySQL functions, but that will require a lot of processing and slow
your queries down. You'll be back where you started, with a solution
that doesn't scale well.
Bob Hall
Know thyself? Absurd direction!
Bubbles bear no introspection. -Khushhal Khan Khatak
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