Given:

DB-A Table 1:
Col. a- 1 2 3 4 5 6 7 1
Col. b- 3 4 5 3 4 5 2 4

It has a PK on Col. a

Step 1:
I create copy of table (with out data) in DB-B Table 1, PK on Col. a is enabled:

Step 2:
When I try to copy data from DB-A Table 1 to DB-B Table 1, the insert into DB-B Table 1 complains about uniqueness. As I have listed the values of Col. a (in DB-A), there ARE 2 rows with the value '1' - so it violates the uniqueness.

My questions was: So why is there duplicate data in Col. a DB-A when it has a PK on it ?

I thing the answer is: that it was probably created with 'novalidate' ???