On 2016/09/15 5:53 PM, David Bicking wrote:
I have two tables:
CREATE TABLE M ( CombineKeyFields, EvtNbr, TransDate, OtherFields, PRIMARY 
KEY(CombinedKeyFields, EvtNbr, TransDate));CREATE TABLE E  ( CombineKeyFields, 
EvtNbr, TransDate, OtherFields, PRIMARY KEY(CombinedKeyFields, EvtNbr, 
"CombinedKeyFields" is shorthand for a combination of about a half dozen fields in the 
primary key."TransDate" is an integer storing a proprietary date sequence number, where 
an older date is always less than a newer date
Now, I want to do E LEFT JOIN M
(1) The CombinedKeyFields must always match in each table(2) Match using the 
EvtNbr, but if no match, use the lowest M.EvtNbr that matches the 

(3) Match using the TransDate but if no exact match, match on the M.TransDate 
that is less than the E.TransDate but greater than the prior E.TransDate
For M.TransDate = 94E.TransDate = 96 will match to 94but E.TransDate = 98 will 
have no match because 94 is less than the prior trans at 96..The idea is to 
find the closest date that matches that couldn't be matched to another record.

Hi David,

I was going to do this for fun, but some anomalies exist in your description which needs to be understood first.

1 - Does every entry have an EvtNbr? Or can it be null? What is the lowest EvtNbr in every set - 1 or 0 or something else or indeterminate? If an EvtNbr cannot be Null, then point (3) above is moot because there will be no item with a date that matches CombinedKeyFields that doesn't also have a lowest EvtNbr as can be matched by requirement (2). If the lowest EvtNbr for any entry is 0 or 1 then you can simply look for that EvtNbr if a match is not found for the exact EvtNbr - which would always exist unless there are NO matches on CombinedKeyFields in which case there should be no matching lines at all as given by (1).

Perhaps if you could (as suggested by another poster) send a full schema with some data and an example of the output needed (highlighting all the possible check cases as described above).

If clarity on these can be had, the SQL is quite possible and not too convoluted even (though the jury is out on efficiency as yet).

Saying a prayer that the email gods won't wrap all these lines together in to 
an unreadable mess like the last time I asked for advice here...

Apparently prayer is not an effective technology :) The e-mail Gods are not at fault here, perhaps the "Send as" settings in your mail composition client can be explored? Many formats should accommodate correct formatting. I'm guessing your client has a plain-text editor that wraps the result into an HTML paragraph (or some other weirdness that you can hopefully deduce and fix by checking the settings).

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