Re: SQL Exists for Flag

[Michael Ryan <michaelrtr@xxxxxxxxx>]

I certainly was! I don't know why I can't get my head around this stuff
sometimes. Maybe it's a vitamin deficiency.


On Thu, Jun 20, 2013 at 1:42 PM, Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx>wrote:

> Woohoo! You made me almost do a happy dance!
>
> ----- Original Message -----
> 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!
> > > > --
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