Subject Re: [IBO] ibo_cursor
Hi Helen,

Question, in your opinion would a server procedure with an
IF (EXISTS .... the way be of the simular speed as no procedure,
but just NOT QUERY.IsEmpty of the type 'SELECT FIRST 1 FROM' ?

From source to server would probably be about the same, but I
wonder about time execution in the server.

Best Regards


Helen Borrie wrote:
> At 10:31 PM 06-09-01 +0000, you wrote:
> >Simple question from a simple mind.
> >What is the absolute fastest way of determining whether a big table
> >has a particular record ?
> >
> >Suppose we have table with columns A,B,C, and D of which A is primary
> >key.
> >Can do, "select Count(A) from mytable where B=5 and C=6 and D=7" say
> >and if count is 0 we have no such record.
> Avoid counts for this task (too expensive).
> >Or can do "select A from mytable where B=5 and C=6 and D=7" and if A
> >is null we have no such record.
> If you only need to know whether the row exists but you don't need a dataset, this can be an approach. But an empty dataset will not return NULL for A, it simply returns nothing. Use a TIB_Cursor, call its First method (not Open) and test for EOF. If True, the set is empty.
> >Or Locate ... ??
> >Having to do many of these within a loop it is desirable to fnd the
> >fastest.
> The very fastest would be to test it by using a TIB_DSQL over a stored procedure that uses EXISTS():
> create procedure R_U_THERE( ArgB integer, ArgC integer, ArgD integer)
> returns (Response smallint)
> as
> begin
> if ( EXISTS ( select A from mytable where B= :ArgB and C= :ArgC and D= :ArrD)) then
> Response = 1
> else
> Response = 0;
> end
> On your client, you might want to create a function to call it:
> function Datamodule1.R_U_There(B, C, D: integer): Boolean;
> begin
> with ib_dsql1 do begin
> if not prepared then
> Prepare;
> Params[0].Value := B;
> Params[1].Value := C;
> Params[2].Value := D;
> Execute;
> if Fields[0].Value = 1 then
> Result := True;
> end;
> end;
> rgds,
> Helen
> All for Open and Open for All
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