Re: NEWBIE: How do I get the oldest date contained in 3 tables

Tom Lane wrote:
> "Dann Corbit" <DCorbit@connx.com> writes:
>>> owner@postgresql.org] On Behalf Of Lorenzo Thurman
>>> I have three tables using date fields. I want to retrieve the oldest
>>> date contained in the tables. Can someone show me an example of a query
>>> that would do that?
>
>> Just do a union and return the min
>
> That's probably not enough detail for a newbie ...
>
> SELECT min(x) FROM
> (
>  SELECT min(datecol1) AS x FROM table1
>  UNION ALL
>  SELECT min(datecol2) AS x FROM table2
>  UNION ALL
>  SELECT min(datecol3) AS x FROM table3
> ) ss;
>
> Exercise for newbie: which of the AS clauses are redundant?
>
>             regards, tom lane
>
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Um, all of them?