Re: Query with conditional statement

Hi Jorge,
You can not use the case statement like in your code.

If you want to get a different field's value by your condition you can use
the case statement like the following examples.


select id,CASE WHEN condition1 THEN fldx1 END AS a1,CASE WHEN
condition1 THEN fldx2 END AS a2,CASE WHEN condition1 THEN fldx3 END AS
a3,CASE WHEN condition2 THEN fldy1 END AS b1,CASE WHEN condition2 THEN
fldy2 END AS b2,CASE WHEN condition2 THEN fldy3 END AS b3FROM
your_table


If you use like above, you have lots of null values.

If you don't have to use column names like a1, a2,a3, b1,b2, or b3 like in
your code, I suggest using like the following

selectid,CASE         WHEN condition1 THEN fldx1         WHEN
condition2 THEN fldy1         ELSE aaa1END AS a1,CASE         WHEN
condition1 THEN fldx2         WHEN condition2 THEN fldy2         ELSE
aaa2END AS a2,CASE         WHEN condition1 THEN fldx3         WHEN
condition2 THEN fldy3        ELSE aaa3END AS a3FROM your_table


Shane Borden <sborden76@gmail.com>, 14 Eyl 2023 Per, 01:43 tarihinde şunu
yazdı:

> You will need to do a CASE statement for each column.  I’m not aware of
> being able to return multiple columns from one case.
>
> Shane Borden
> sborden76@gmail.com
> Sent from my iPhone
>
> On Sep 13, 2023, at 4:23 PM, Tchouante, Merlin <mtchouan@umaryland.edu>
> wrote:
>
> 
>
> Yes, it can.
>
>
>
> *Thanks,*
>
> *  -- Merlin*
>
>
>
>
>
> *Merlin D. Tchouante,* Sr. IT Enterprise Application Developer
> *Center for Information Technology Services (CITS)*
> *601 West Lombard Street*
> *Baltimore, Maryland 21201-1512*
> *mtchouan@umaryland.edu* <mtchouan@umaryland.edu>
> 410-706-4489 * 410-706-1500 fax
>
>
>
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> <image001.png>
>
>
>
> *From:* JORGE MALDONADO <jorgemal1960@gmail.com>
> *Sent:* Wednesday, September 13, 2023 1:52 PM
> *To:* pgsql-sql@postgresql.org
> *Subject:* Query with conditional statement
>
>
>
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>
> Hi,
>
>
>
> Can a conditional CASE statement be part of the SELECT portion of a query?
> For example:
>
>
>
> SELECT
>
> fld1, fld2, fld3,
>
> CASE
>
>     WHEN condition1 THEN fldx1 AS a1, fldx2 AS a2, fldx3 AS a3
>
>     WHEN condition2 THEN fldy1 AS b1, fldy2 AS b2, fldy3 AS b3
>
>     ELSE .....
>
> END,
>
> fld6, fld7
>
> FROM ......
>
> WHERE ......
>
>
>
> I ran a test and see the following:
>
> * Each WHEN only accepts 1 result and not 3 as shown in the example
>
> * The AS for the alias is not supported
>
>
>
> I need to return more than 1 field on each WHEN and also assign an ALIAS.
>
> I very much appreciate your feedback.
>
>
>
> Regards,
>
> Jorge Maldonado
>
>