So did I get it right? You have both shown tables in you DB and you have a third table in a text file containing an idCars combined with an idSize, so something like this:

idCars   idSize
------   ------
1        3
1        2
2        1
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And you want to get:

Car          Size
----------   ----------
MiniCooper   sedan
MiniCooper   compact
Civic        subcompact
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I'd create a new table CarSize with the content of your text.

The query (your vlookup) would then be something like this:

select Car, Size
from CarSize
join Cars
using(idCars)
join Size
using(idSize)
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Note: Untested SQL Code I'd write for Oracle. The join-syntax might vary on mySQL.