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Re: (somewhat OT) Seeking a SQL counter-example

by extremely (Priest)
on Feb 28, 2007 at 21:26 UTC ( #602600=note: print w/ replies, xml ) Need Help??


in reply to (somewhat OT) Seeking a SQL counter-example

IDSalesIDCityIDMoney
110201000
210222000
311204000
411228000
510203000
610225000
711207000
811229000

select from table SalesID,CityID,Sum(Money) Groupby SalesID,CityID -- or select from table SalesID,CityID,Sum(Money) Groupby CityID, SalesID

Those should vary only in output order of the summed rows. The danger of automatic grouping is when/if someone picks "ID" in the select list... then it all goes to heck. The "common case" for Group By is to list all columns not aggregated in the select_column clause. Automatically forcing group-by seems to be almost assuredly doomed to run into keys and foreign-keys when they are incorrectly added to the columns list.

In your limited case, tho, I'm thinking you're safe.

--
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Re^2: (somewhat OT) Seeking a SQL counter-example
by dragonchild (Archbishop) on Feb 28, 2007 at 21:40 UTC
    Assuming that ordering is unimportant (because if ordering is important, you'll put an ORDER BY clause in), then does this mean that automagical grouping if there is a function that requires it (count, max, min, sum, etc) is bad or ok?

    My criteria for good software:
    1. Does it work?
    2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

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