RE: Using SQL to check for duplicate records

Booth:

That's where count(*) comes into it. Rob's example shows that a second SELECT 
statement must also be executed. In effect, a new temporary table is created on 
the fly by that SELECT. That table contains one row for each key that's 
duplicated. When the primary SELECT executes, each row is tested against the 
temporary table to see if he's dealing with a duplicated key or not. If he is, 
he simply prints the key and the RRN. The temporary table fulfills almost the 
same function as lookahead would -- it simply verifies duplication for each row 
at the time the row is read.

If the temporary table happens to be very large, conceivably you could have 
space problems. Unlikely enough that I wouldn't worry about it unless I was 
dangerously short on space and expected a lot of duplicates.

Tom

midrange-l-request@xxxxxxxxxxxx wrote:

>   9. RE: Using SQL to check for duplicate records (Booth Martin)
>
>One question I have about the SQL solution is about printing the results.
>When/how does one print the RRN of all duplicate records using only SQL?
> 
>-------Original Message-------
> 
>In SQL, just getting count(*) for the groups could take a chunk of
>processing. I'm not sure it could be any more efficient in any other
>language.


-- 
Tom Liotta
The PowerTech Group, Inc.
19426 68th Avenue South
Kent, WA 98032
Phone  253-872-7788 x313
Fax    253-872-7904
http://www.powertech.com


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