Tricky Trigger

[ligang]

I have a transaction table which is increasing 300K records every month .

let's say the PK of this table is C1+C2+C3

And now I want to write a trigger to extract distinct C1+C2
into another table .

My problem is as the number of C1+C2 is much less than the number of C1+C2+C3 , ( 1%) and the trigger is fired by row level
so in the trigger I have to check whether C1+C2 has been already inserted into the table , that is pain .

T1: T2:
C1 C2 C3A ---> Insert C1 C2
C1 C2 C3B ---> Check Existence , NO insertion
C1 C2 C3C ---> Check Existence , NO insertion
C1 C2 C3D ---> Check Existence , NO insertion

Any good solution to make it simple ?

[marist89]

sure, always insert c1 + c2 and catch the DUP_VAL_ON_INDEX in a EXCEPTION block and then ignore it.

[ligang]

how is the performance consideration in this case?

[marist89]

You have a business requirement, right?