How to overcome Netezza's lack of unique constraint/referential integrity enforcement?

Question

It appears that the lack of support for enforcing 2 basic constraints (unique and foreign key), is a reason for loss of many man-hours debugging and troubleshooting difficul

Answer 1

Why not add a column that is a hash value of the columns to which you wish to apply the constraint? The NZ SQL extensions package has hashing functions. If you use hash8('key') where 'key' is a concatination of your constrained column values (cast to varchar) then you get a probably unique BIGINT value. I say 'probably' because the probability of hash collision is finite all-be-it low. If you need a stronger gaurantee of uniqueness you can use the cryptographic-level 'hash()' function instead.

Unless you have really huge quantities of data however, hash8 should be the better choice. Since it gives integer values, comparison of rows is a matter of simple arithmatic and as such is fast. So for example you can just update or insert rows on the basis of the hash value, which is just an integer comparison.