topic Re: tMap - Match Model - Problem with design of this option in Talend Studio

tMap - Match Model - Problem with design of this option

Winfried_Hoesmann — Tue, 18 Jun 2024 11:49:17 GMT

Hi,

can anybody explain me why talend design the Match Model as it is?

First - There is an option "First match" which matches the first record of the lookup table. All fine, easy to understand for me and works as it sounds.

Second - The option "All matches" matches all records with the same key, it is also is fine to understand and use for me.

Third - The option "Unique match" matches the last record of the lookup table. I am not a english speaking man, may be I dont know the meaning of "Unique" at all. But for me I never thought that that means to match the last record. If we have an option "First match", why not to name this option "Last match"? And - why is this default? For me as SQL joiner, All Matches makes more sense.

Fourth - "All rows" - Why don't use All matches without key instead? Then no 4th Option is used.

Re: tMap - Match Model - Problem with design of this option

Xiaodi_Shi — Wed, 19 Jun 2024 04:55:23 GMT

Hello,

The "Unique" will match with the last key into the lookup, then if you have several rows with the same key, the last will match ( Unique and Last options had been merged as only "Unique match" since V Talend 3.1, a quite old version).

Contrary to the "First match" which will match with the first loaded row into the lookup if several rows have same key.
"All matches": If several matches are found in the Inner Join, i.e. rows matching the explicit join as well as the filter, all of them will be added to the output flow

For example:

Main Table:
id;name
1;Sabrina
2;plegall

Lookup Table:
id;age
1;11
1;12
1;13
2;21
3;31

Do a inner join with id key and output id, age column.
Unique match(has the same behavior with last match)
1;13
First match, get:
1;11
All match, get:
1;11
1;12
1;13

Our Documentation is heavy on tMap so you should what you want from there.

https://community.qlik.com/t5/Official-Support-Articles/Doing-an-inner-join-using-a-tMap-component/ta-p/2150835

https://help.talend.com/en-US/components/8.0/talend_components/st-tmap-scenario-link

Best regards

Sabrina

Re: tMap - Match Model - Problem with design of this option

Winfried_Hoesmann — Mon, 24 Jun 2024 06:11:51 GMT

Hi,

thank you for explaining how it works, but I know how it works. What I want is to know why is the naming of the options. That is misleading for me.

"unique" should go on a error, if there is more than one record matching.

On my side it as a bad decision to merge last and unique options.

Regards Winfried