May 2018
Intermediate to advanced
576 pages
30h 25m
English
It's possible to have uniqueness in a set of columns without creating an index. That might be useful if all we want is to ensure uniqueness rather than allow index lookups.
To do that, you can do either of the following:
Each of these will provide a unique value for use as a row's key. The uniqueness is not enforced, nor will there be a unique constraint defined. So there is still a possibility that someone might reset the sequence to an earlier value, which will eventually cause duplicate values.
Consider also that this method provides the unique value as a default, which is not used when the user specifies an explicit ...