I have the following SQL understanding problem concerning UPDATE :
I have two tables I want to join over a new artificial key a_id.
The tables can already be joined over an existing alternate key.
select a.a_id from a,bwhere a.custno = b.custno
=> selects about 1000 id's
b.a_id so far only holds NULL values and should be updated to hold the
correct foreign key references to a.a_id.
+-------------------+
| a |
|-------------------|
| a_id prim. key |0---+
| custno altern.key| |
+-------------------+ | | mc +----------------+
| b | +----------------+ | b_id prim.Key | | a_id
forgn.Key| 1 custno | +----------------+
What i want to do is something like this :
------------------------------------------
update b
set b.a_id = a.a_id
where b.custno = a.custno;
or is that the right way to do it :
update b
set b.a_id = (select a.a_id from a,b where a.custno = b.custno)
where b.custno in (select a.custno from a);
I just seem to use the UPDATE not correctly, it cannot be parsed.
What is the correct solution to this ?
Can anyone help ?
I know that's a RTFM but I have no FM to R.
Is there a good SQL tutorial/reference ?
ThanX
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Christian Rudow E-Mail: Christian.Rudow@thinx.ch
ThinX networked business services Stahlrain 10, CH-5200 Brugg
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