Re: Using SQl to obtain a field value from one file or another

So, if he uses left outer join (or just left join) he'll have to do all
that null checking stuff. However if he uses left inner join he should be
good?


Rob Berendt
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From: Charles Wilt <charles.wilt@xxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Date: 06/30/2017 04:47 PM
Subject: Re: Using SQl to obtain a field value from one file or
another
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



left join == left outer join

Charles

On Fri, Jun 30, 2017 at 2:32 PM, Rob Berendt <rob@xxxxxxxxx> wrote:

Is
left join = left outer join
or
left join = left inner join.


Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: Mike Jones <mike.jones.sysdev@xxxxxxxxx>
To: midrange-l@xxxxxxxxxxxx
Date: 06/30/2017 03:55 PM
Subject: Re: Using SQl to obtain a field value from one file or
another
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



Re:

select coalesce( nullif( FILE1.FIELD1, '' ), FILE2.FIELD1 ) as FIELD1
,coalesce( nullif( FILE1.FIELD2, '' ), FILE2.FIELD2 ) as FIELD2
from ...

NULLIF may not be needed in Alan's case, but it is needed in cases where

a

row is retrieved as part of the FROM table or a LEFT JOIN table, and the
column value is non-null, but blank, and you want to ignore blanks (i.e.
you want to deliver the first non-blank value).

COALESCE used alone will deliver blank values, which may be desired in
some
cases, and not others.

NULLIFs inside COALESCEs is a common technique used on many databases,

not

just ours.

Reminder: COALESCE handles cascading through many values, not just two

as

in the above example.

Mike

message: 4
date: Fri, 30 Jun 2017 19:19:41 +0000
from: Tommy Holden <Tommy.Holden@xxxxxxxxx>
subject: RE: Using SQl to obtain a field value from one file or
another

The nullif() isn't required as coalesce will handle that for you.

Select file1.field1, coalesce(file2.field2,file3.field2) from...


Thanks,
Tommy Holden

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