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On 2/15/11 6:44 AM, David FOXWELL wrote:
I need to find if a transaction of a particular type and amount
exists for a client.
I cannot remember how to apply the SQL Exists( ) to look for the
transaction.
Select '1' from ????
where exists ( select * from mytable
where myfield = 'myfield')
<<SNIP>>
select '1' /* or e.g. left(char(count(*)),1) */
from qsys2/qsqptabl /* sysdummy1 equivalent */
where exists ( select '1'
from mytable
where TransType=:TT
and TransAmnt=:TA )
If there is an INDEX with TransType and TransAmnt as [the leftmost]
keys, then the access could be "index-only" against the "mytable" data
to validate existence. That SQL would perform almost as fast or even
faster than a SETLL across repeated requests [since building the access
plan and first open], for various replacement values for the
transaction-type and transaction-amount variables.
Regards, Chuck
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