What is difference between Primary Key, Unique Key and candidate key?
+3
A:
Google does not work anymore?
Alex Reitbort
2010-09-01 10:24:58
+2
A:
Candidate key is a minimal (i.e. irreducible) key, unique key is a pleonasm, and primary key is an obsoleted concept still surviving from the days when people thought it possible for one key to be "more unique" than any of the others.
Erwin Smout
2010-09-01 11:12:27