Domain and Data Dependency

DOMAIN-

A domain in DBMS is a unique set of values permitted for an attribute in a table. For example, a domain of week-of-days can accept Monday, Tuesday, ...., Sunday as possible values, a domain of integers can accept whole numbers that are negative, positive, and zero.

DATA DEPENDENCY-

Dependencies in DBMS is a relation between two or more attributes. In more simple terms we can say that some data values are dependent on other data values in order to get recognized.

Example-

Roll no→ name

In this example Roll no. will be unique for each student but two students can have the same name. Suppose we want to know about the student whose name is Amit but there are two students with the name Amit, so in this case, the name doesn’t uniquely identifies the student(we have confusion about which student’s information we want). But if we take Roll no.(say 101) then we will get information from one student whose name is Amit and Roll no. is 101, hence no confusion. Therefore the name is dependent on Roll no.

It has the following types in DBMS −

• 1. Functional Dependency
• 2. Fully-Functional Dependency
• 3. Transitive Dependency
• 4. Multivalued Dependency
• 5. Partial Dependency