Re: HELP WITH A QUERY

On 2010-11-24, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:
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> I have 2 tables and each one has a date field. Is it possible to write a
> simple query to get the records with the dates in table1 but not in table2?
> For example:
>
> TABLE 1
>
> -----------------------------------------------------------------------------
> Branch_Name    Sales    Date
> -----------------------------------------------------------------------------
> Los Angeles        1500     May-15-2010
> San Diego            250      May-27-2010
> Los Angeles         300      May-28-2010
> Boston                 700      May-28-2010
>
>
> TABLE 2
>
> -----------------------------------------------------------------------------
> Date                       Sales
> -----------------------------------------------------------------------------
> May-27-2010             250
> May-20-2010             535
> May-21-2010             320
> May-22-2010             750



> The query result should be:
> May-15-2010
> May-28-2010

all examples untested

eg "NOT IN":

 select date from table1 where date not in ( select distinct date from table2);

or this "LEFT JOIN WHERE NULL:

select table1.date from table1 left outer join table2 on
table2.date=table1.date where table2.date is null.

or this "EXCEPT":

select date from table1 except select date from table2

If you want a tested example make it easy for us, post the SQL to make those
tables.

> I guess that a query with a subselect and the EXCEPT keyword would work but
> I would like to know if there is a simpler alternative?

EXCEPT is probably the best way, but all three methods will probably
produce similar query plans and have similar performance.

except is not really a subquery as both queries are on the same level.
"not in" uses a subquery.

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