Update ... from ...

Hello.

I am a little lost... in the use of update ... from ...

Let us assume I have something like this:

UPDATE parts SET id_geometry = b.id_geometry_duplicate
FROM
parts a
INNER JOIN fn_duplicate_parts(@id_project) b ON a.id_part = b.id_part_org

How does this query know which rows it needs to update? I can see no relationsship between the tables parts and b (which by accident is also parts). I only want to update those rows in parts where id_part is in b(as id_part_org). I guess it is my lack of knowledge, but really I cannot see the logic in this.

Could anyone clarify?

Thanks in advance,

Lasse Johansen

when you say inner join it's kind of like making it one table on the ON part, so if your tables are


the inner join on makes them equal on id, in this case lets say id is the circle, square rhombus name portion

so our table after the inner join is this

and you're setting A. price equal to B.price, so it turns into

so your final A table is

Actually this is not my concern... My concern is how can parts a(in FROM(SELECT) clause) refer to parts(in UPDATE clause)