Re: SQL "like" from a subselect (Roger Harman)

Hi Roger,

I tend to use this design pattern for matches like that, when there is more
than one row to match, and I want to pick only one row match out of many.
This give you the flexibility to pick which single row out of many matches
to include in the set:

select A.*, SN.SRCHNAME
from TABLE_A A
cross join lateral (
select SN.SRCHNAME
from NAMEFILE SN
where lower(A.UPTEXT) like SN.SRCHNAME
order by [add column(s) here to prioritize which matching row to select]
--or remove the order by to randomly pick one row
fetch first row only --pick only one row
) as SN

Note: CROSS JOIN will discard rows from TABLE_A without a match. Use LEFT
JOIN instead if you want all TABLE_A rows in the set, regardless if a match
is present or not.

Add this to the query if you want a count of the matches:

cross join lateral (
select count(*) as MATCH_COUNT
from NAMEFILE SN
where lower(A.UPTEXT) like SN.SRCHNAME
) as CNT

...along with adding CNT.MATCH_COUNT to the SELECT column list.

This mini eBook will teach you everything you're likely to want to know
about this technique:
https://drive.google.com/file/d/0B86kLoHq8E_PeVlhNmZORmpBUjA/view?usp=sharing

Mike

date: Wed, 25 Nov 2015 19:38:54 +0000
from: Roger Harman <roger.harman@xxxxxxxxxxx>
subject: SQL "like" from a subselect

I'm trying to match employee names (first or last) to text in the user
profile. ?It's just a rough match to help operations in a task.

I have all the first & last names in a file and the user profile info in
another.

I've tried "where lower(UPTEXT) like (select srchname from namefile)" but
it fails with SQL0811 "Result of SELECT more than one row".

The search names are in the form of "%roger%". ?I can match singles in
STRSQL.

I can whip up an RPG with %scan() but curious if?I can?make the subselect
work. ?There are hundreds of profiles and thousands of employees.

Thanks in advance.


Roger Harman
COMMON Certified Application Developer - ILE RPG on IBM i on Power
OCEAN User Group