satisfies algorithm
From: <aarklon_at_gmail.com>
Date: Fri, 25 Jul 2008 05:41:53 -0700 (PDT)
Message-ID: <94535fa5-c35a-4eb7-a975-294496da668d_at_z11g2000prl.googlegroups.com>
Hi all,
Date: Fri, 25 Jul 2008 05:41:53 -0700 (PDT)
Message-ID: <94535fa5-c35a-4eb7-a975-294496da668d_at_z11g2000prl.googlegroups.com>
Hi all,
the following is the algorithm which i saw in schaum series book(fundamentals of relational databases)
satisfies algorithm
this algorithm shown below can be used to determine if a relation r satisfies or does not satisfies a given functional dependency A -> B. the input to the algorithm is a given relation r and a functional dependency A -> B. the output of the algorithm is true if r satisfies A -> B; otherwise the output is false.
- sort the tuples of the relation r on the A attribute(s) so that tuples with equal values under A are next to each other
- check that tuples with equal values under attribute(s) A also have equal values under attribute(s) B
- if any tuples of r meet condition 1 but fail to meet condition 2 the output of the algorithm is false. otherwise, the relation satisfies the functional dependency and the o/p of the algorithm is true.
now my question is there any other better method (other than inference axioms) ? Received on Fri Jul 25 2008 - 14:41:53 CEST