Re: CHAIN Versus SETLL and READ When Data Needed

Barbara Morris wrote on 28/02/2007 07:54:42 PM:

You could use a list of keyfields like 
Dennis suggested; but I think the keyds is _slightly_ better than a list 

of keyfields _in this case_, since it's a bit easier to see that the 
same key ds is being used for each CHAIN in the group (only one name to 
check vs a list of 3 names or values).

I'm glad I re-read your message more carefully, because on first skim I 
thought "Why KDS instead of (keyFld1 : keyFld2 : keyFld3)".

D keyds         e ds        extname(file:*key)
  /free
    keyds.fld1 = something;
    keyds.fld2 = somethingelse;
    keyds.fld3 = whatever;
    chain %kds(keyds:3) file;
    if %found
       ...
    else;
       chain %kds(keyds:2) file;
       if %found
           ...
       else;
          chain %kds(keyds:1) file;

I also thought of another way that this could lend itself to being better 
than a list of key fields.  Consider:

for numToCheck = NUM_KEY_FIELDS down to 1;
    chain %kds(keyDS : numToCheck);
    if (%found());
        leave;
    endif;
end for;


Firstly, if the number of key fields changes, all that is required is to 
change the NUM_KEY_FIELDS constant.  Perhaps there is even a way to 
determine the number of key fields programmatically?  Secondly, just to 
fan the flames again ... maybe this is a good case for the leave opcode? 

:)

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