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Performance issues with concatenation operator [message #369395]

Tue, 12 September 2000 14:37

Gerard Vaz
Messages: 9
Registered: September 1999

Junior Member

Is it true that the performance of a query degrades if the columns being selected are concatenated (in my case they are just two columns)? If so, how significant is the degradation?

What about if the columns are indexed?

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Re: Performance issues with concatenation operator [message #369423 is a reply to message #369395]

Tue, 19 September 2000 11:39

Melissa
Messages: 65
Registered: January 2000

Member

When concatenation is used in a query, the indexes are not accessed resulting in full table scans.

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Re: Performance issues with concatenation operator [message #369449 is a reply to message #369395]

Fri, 22 September 2000 17:43

pat
Messages: 27
Registered: September 2000

Junior Member

I think its only a problem if you are doing the concatenation in the where clause

i.e. WHERE COL1 || COL2 = 'XYZ'

If the concatenation is just in the SELECT portion, then it shouldn't affect which indexes are used.

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