Re: SQL Exists for Flag

[Michael Ryan <michaelrtr@xxxxxxxxx>]

Wonderful...it works! Thanks Vern (and Charles). Seeing the straight select
with the left outer join helped me see it Vern. Yay!


On Thu, Jun 20, 2013 at 1:33 PM, Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx>wrote:

> Hi Michael
>
> Let's see if I can make sense of this - a LEFT OUTER JOIN gives you all
> records from the first table, plus any matching records from the second
> table.
>
> So the JOIN accomplishes the EXISTS condition. If FLD1 exists in TableB,
> there will be values there.
>
> When there is not a matching record - FLD1 is not in TableB, then the
> column TAbleB/Fld1 will be NULL. So the CASE tests for that and sets either
> 'X' or a blank.
>
> You can get a better feel for it, perhaps, if you run this -
>
> select tablea.fld1, tablea.fld2, tableb.fld1 from tablea left outer join
> tableb on tablea.fld1 = tableb.fld1
>
> If I'm guessing right, you should see some hyphens in the 3rd column -
> these are the NULLs for unmatched records.
>
> Vern
>
> ----- Original Message -----
> Hey Vern -
>
> But the condition isn't that TableB.Fld1 is null, it's that the key value
> TableA.Fld1 is found in TableB.
>
>
> On Thu, Jun 20, 2013 at 1:01 PM, Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx
> > wrote:
>
> > Hi Michael
> >
> > That's what this should do - a LEFT OUTER JOIN will give you all records
> > from TableA and TableB, if there is a match - NULLs, otherwise.
> >
> > Give it a try. You might like it almost as much as 7Up!
> >
> > Vern
> >
> > ----- Original Message -----
> > Thanks guys...I didn't explain myself well. I want to display the values
> > from TableA, and an 'X' if the key in TableA is found in TableB.
> >
> >
> > On Thu, Jun 20, 2013 at 12:27 PM, Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx
> > > wrote:
> >
> > > Left outer JOIN, I think.
> > >
> > > select tablea.fld1, tablea.fld2, case when TableB.fld1 is null then ' '
> > > else 'X' end from tablea join tableb on tablea.fld1 = tableb.fld1
> > >
> > > Check the syntax of the CASE - I'm doing this from memory.
> > >
> > > HTHAW (hope this helps and works)
> > > Vern
> > >
> > > ----- Original Message -----
> > > Here's what I want to do...TableA has 4 columns. TableB shares a key
> > value
> > > with TableA. I want to produce this output in a select statement (to be
> > > used from PHP fwiw):
> > >
> > > TableA.Fld1 TableA.Fld2 'X' (if TableA.Fld1 is in TableB).
> > >
> > > I've been trying combinations of a CTE, CASE, and exists, but I can't
> get
> > > this to work. I'd like:
> > >
> > > A1 A2
> > > A3 A4 X
> > > A5 A6 X
> > > A7 A8
> > >
> > > IOW, I want the values for TableA to show up, and an X if the
> > corresponding
> > > key value is in TableB. This has to be easier than I'm making it out to
> > be.
> > > Thanks!
> > > --
> > > This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
> > list
> > > To post a message email: MIDRANGE-L@xxxxxxxxxxxx
> > > To subscribe, unsubscribe, or change list options,
> > > visit: http://lists.midrange.com/mailman/listinfo/midrange-l
> > > or email: MIDRANGE-L-request@xxxxxxxxxxxx
> > > Before posting, please take a moment to review the archives
> > > at http://archive.midrange.com/midrange-l.
> > >
> > > --
> > > This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
> > list
> > > To post a message email: MIDRANGE-L@xxxxxxxxxxxx
> > > To subscribe, unsubscribe, or change list options,
> > > visit: http://lists.midrange.com/mailman/listinfo/midrange-l
> > > or email: MIDRANGE-L-request@xxxxxxxxxxxx
> > > Before posting, please take a moment to review the archives
> > > at http://archive.midrange.com/midrange-l.
> > --
> > This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
> list
> > To post a message email: MIDRANGE-L@xxxxxxxxxxxx
> > To subscribe, unsubscribe, or change list options,
> > visit: http://lists.midrange.com/mailman/listinfo/midrange-l
> > or email: MIDRANGE-L-request@xxxxxxxxxxxx
> > Before posting, please take a moment to review the archives
> > at http://archive.midrange.com/midrange-l.
> >
> > --
> > This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing
> list
> > To post a message email: MIDRANGE-L@xxxxxxxxxxxx
> > To subscribe, unsubscribe, or change list options,
> > visit: http://lists.midrange.com/mailman/listinfo/midrange-l
> > or email: MIDRANGE-L-request@xxxxxxxxxxxx
> > Before posting, please take a moment to review the archives
> > at http://archive.midrange.com/midrange-l.
> --
> This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
> To post a message email: MIDRANGE-L@xxxxxxxxxxxx
> To subscribe, unsubscribe, or change list options,
> visit: http://lists.midrange.com/mailman/listinfo/midrange-l
> or email: MIDRANGE-L-request@xxxxxxxxxxxx
> Before posting, please take a moment to review the archives
> at http://archive.midrange.com/midrange-l.
>
> --
> This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
> To post a message email: MIDRANGE-L@xxxxxxxxxxxx
> To subscribe, unsubscribe, or change list options,
> visit: http://lists.midrange.com/mailman/listinfo/midrange-l
> or email: MIDRANGE-L-request@xxxxxxxxxxxx
> Before posting, please take a moment to review the archives
> at http://archive.midrange.com/midrange-l.