Re: question about queries

Jason Grace wrote:
>
> Lets say you have 3 tables, table A table B and table C.
>
> Say table A has info for different id's such as salary, name etc, on a
> one line per person basis. say for each line, there corresponds
> multiple lines in table B for that id, and similarly for table c.
>
> Now say tables A B and C have values valA, valB, and valC respectively
> as fields (for instance salary, payments), and I want to sum up these
> values for a given month.
>
> What is the fastest most efficient way to do this correctly?

  Suppose there are three tables: a, b, c.   The structure is a(i number , v number ), b(i number , v number ),   c(i number, v number). The distribution of the values is same as the   problem specified. You can solve your problem by using the following   query:

  select sum(a.v)/count(*), sum(b.v)/count(distinct(c.rowid)), sum(c.v)/count(distinct(b.rowid)) from a,b,c where a.i=b.i and b.i=c.i;

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