Re: CTE in SQL

[Charles Wilt <charles.wilt@xxxxxxxxx>]

No.

A CTE only exists for a single statement.

DECLARE GLOBAL TEMPORARY TABLE allows you to build a work file that can be
used by multiple statements.  But there's significant downsides to doing
so, namely the fact such a table has no indexes.  You can of course add
some before you start working with it.  In general, IBM recommends staying
away from them as they are easily abused.  (see
https://www.itjungle.com/2015/06/02/fhg060215-story02/) But they do make
sense sometimes.

In your example, there's really no need for either two statements or even
the CTE
select fld01
  from table1
where fld3 = 'ABCD'
         and fld2 in ('X','Z');

Now maybe it was a simple example, and the above won't work for real...or
maybe you're just experimenting with CTE's.

UNION (or preferably UNION ALL) as Carel suggests is something to keep in
mind to join together the results of two separate SELECT.

Charles


On Thu, Jun 3, 2021 at 2:21 PM K Crawford <kscx3ksc@xxxxxxxxx> wrote:

> I am teaching myself the CTE of SQL.  Got it working great.  Have one
> question.
> I have one CTE that I want to use for two separate  SQL statements.
> In ACS Run SQL Scripts it would look something like this.
>
> with cte_temp as (
>      select fld01, fld02
>      from table1
>      where fld3 = 'ABCD'
>      )
> select fld01
> from cte_temp
> where fld2 = 'X'
> ;stop;
> select fld01
> from cte_temp
> where fld2 = 'Z'
>
> Can this be done?  I ended up copy the cte_temp to the second SQL.
>
> --
> KCrawford
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