How does Oracle handle repeated calculations? Is it evaluated once or is it evaluated each time it is encountered?
For instance in a case statement creating buckets for counting
CASE
WHEN A Date - Discharge Date < 31 THEN '000-030'
WHEN A Date - Discharge Date < 61 THEN '031-060'
WHEN A Date - Discharge Date < 91 THEN '061-090'
ELSE '091+'
END
Can this be rewritten in the other CASE form as
CASE A Date - Discharge Date
WHEN ???? THEN '000-030'
...
ELSE '091+'
END
I realize the SQL is not in Oracle SQL format. My question is on the substance as the tool I use will put it in Oracle format when the query is built.
I know some databases will calculate the A Date - Discharge Date once and others would in this case calculate it 3 times. This is just an example. My real statement I am working with has the calculation repeated 14 times thus my concern for speed
mlmcc
For instance in a case statement creating buckets for counting
CASE
WHEN A Date - Discharge Date < 31 THEN '000-030'
WHEN A Date - Discharge Date < 61 THEN '031-060'
WHEN A Date - Discharge Date < 91 THEN '061-090'
ELSE '091+'
END
Can this be rewritten in the other CASE form as
CASE A Date - Discharge Date
WHEN ???? THEN '000-030'
...
ELSE '091+'
END
I realize the SQL is not in Oracle SQL format. My question is on the substance as the tool I use will put it in Oracle format when the query is built.
I know some databases will calculate the A Date - Discharge Date once and others would in this case calculate it 3 times. This is just an example. My real statement I am working with has the calculation repeated 14 times thus my concern for speed
mlmcc
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