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 ? 

Thank you very much,

chas

ps. using an old version at the moment - 3.22.25




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