# Re: satisfies algorithm

Date: Fri, 25 Jul 2008 08:54:05 -0400

Message-ID: <92kik.14667$cW3.1512_at_nlpi064.nbdc.sbc.com>

<aarklon_at_gmail.com> wrote in message
news: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.
**>
**> 1) 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
**>
**> 2) check that tuples with equal values under attribute(s) A also have
**> equal values under attribute(s) B
**>
**> 3) 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) ?
*