Re: How to write such a query

On 9/18/20 1:18 PM, Igor Korot wrote:
> Hi, Ken,
> 
> On Fri, Sep 18, 2020 at 2:46 PM Ken Tanzer <ken.tanzer@gmail.com 
> <mailto:ken.tanzer@gmail.com>> wrote:
> 
>          > How to find what the primary key (or UNIQUE identifier) value is
>          > for row 5 in the recordset?
> 
>         You're missing the point: as mentioned before, there is no "row
>         5". To
>         update the 5th record that you've fetched, you increment a
>         counter each time
>         you fetch a row, and when you read #5, do an UPDATE X SET field1
>         = 'blarg'
>         WHERE id = <thekeyvalue>;
> 
> 
>     It seems worth mentioning for benefit of the OPs question that there
>     _is_ a way to get a row number within a result set.  Understanding
>     and making good use of that is an additional matter.
> 
>     SELECT X.field1, Y.field2*,row_number() OVER ()*  from X, Y WHERE
>     X.id = Y.id -- ORDER BY ____?
> 
>     That row number is going to depend on the order of the query, so it
>     might or might not have any meaning.  But if you queried with a
>     primary key and a row number, you could then tie the two together
>     and make an update based on that.
> 
> 
> Thank you for the info.
> My problem is that I want to emulate Access behavior.
> 
> As I said - Access does it without changing the query internally (I 
> presume).
> 
> I want to do the same with PostgreSQL.
> 
> I'm just trying to understand how to make it work for any query
> 
> I can have 3,4,5 tables, query them and then update the Nth record in 
> the resulting recordset.

You mean you are doing a join over 5 tables and then updating some 
record that is the output of the join?

If so are you updating all the values or a value or some portion of the 
values?

This is being done in a form or in the query builder?

> 
> Access does it, PowerBuilder does it.
> 
> I just want to understand how.
> 
> Thank you.
> 
> 
>     Cheers,
>     Ken
>     -- 
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-- 
Adrian Klaver
adrian.klaver@aklaver.com