What are the uses of attribute closure A+ / Purposes of finding attribute closure / Attribute closure in DBMS
Several uses of attribute closure:
1. Used to check whether an
attribute (or set of attributes) forms a key or not.
Use the
algorithm discussed in the posts “How to find closure of attributes in DBMS?” Or “How to find key of a given table? - Analternate way”.
2. Used to find easily all the
functional dependencies hold in a relation.
For example,
to check whether a FD like A → B holds in a relation, find the A+.
If B is in A+, then the functional dependency A → B is valid.
3. Used as an alternate way to
find Closure of FDs (F+).
For every
attribute or set of attributes on the left hand side of the arrow in a functional
dependency, find the Closure. This process results in F+.