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Message Posted: Mon, 29 Aug 2005 @ 16:39:30 GMT
CHAR to VARCHAR does not require internal conversion.
INTEGER TO DECIMAL does require conversion, will be stored differently internally.
CHAR(4) to CHAR (5) there is no internal conversion.
BYTE TO INTEGER, hash the same, no conversion required.
There are two performance issues when conversion is required...first the extra CPU used for the conversion during a join, second is extra redistributions, sorting, spooling involved with joins.
Run explains and you will see the difference in your join plans for the cases where conversion is required.
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