Reading from multiple tables

[balachandar]

We have two tables A,B. periodically we are moving data
from A to B(all columns).A and B have the same column name.
at a given point of time, if a record is not there in A, then from B we need to take a record for processing.is there
any easy way to do this.

 

[elmo29]

Use the EXISTS keyword and match up each column, or the PK

i.e.

select * from b where not exists (select * from a where a.pk = b.pk)

you can apply this to in lots of different ways - in if statements etc

So you could have something to the effect

if not exists in A then go to B else goto A