Re: SQL EXISTS predicate

["David Morris" <dmorris@xxxxxxxxxxxxx>]

Rob,

Here are the three equivalent ways to check for unmatched records. The first 
method seems to run the fastest:

Select records in the city master that do not have a matching record in the 
state master:

Select CCITY, CSTATE From CITYMAST Exception Join STATEMAST On CSTATE = SSTATE  
                                                          

Above using sub-select:

Select CCITY, CSTATE From CITYMAST Where Not Exists (Select SSTATE From 
STATEMAST Where CSTATE = SSTATE)

Above using quantified comparison:                                              
              

Select CCITY, CSTATE From CITYMAST Where CSTATE *= All(Select SSTATE From 
STATEMAST)

David Morris


>>> Rob Berendt <rob@dekko.com> 03/08/99 02:05PM >>>
Does anyone have a good example of the SQL exists predicate?  I am having a 
tough time understanding how this is used.


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