**Operational Data Store Interview Questions for freshers experienced :-**

**1. What is normalization? **

It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties

- Minimizing redundancy
- Minimizing insertion, deletion and update anomalies.

**2. Explain DDL (Data Definition Language)? **

A data base schema is specifies by a set of definitions expressed by a special language called DDL.

**3. Explain Functional Dependency? **

Functional dependency is denoted by X –> Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

**4. What is a functional dependency F said to be minimal? **

- Every dependency in F has a single attribute for its right hand side.
- It cannot replace any dependency X –>A in F with a dependency Y–> A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.
- We cannot remove any dependency from F and still have set of dependency that is equivalent to F.

**5. Explain a Relation Schema and a Relation?**

A relation Schema denoted by R(A1, A2, ?, An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, …, tn). Each tuple is an ordered list of n-values t=(v1,v2, …, vn).

**6. What is operational data store? **

An operational data store (or “ODS”) is a database designed to integrate data from multiple sources to make analysis and reporting easier.

**7. What is a Relationship? **

It is an association among two or more entities.

Relationship Set – The collection (or set) of similar relationships.

Relationship Type – Relationship type defines a set of associations or a relationship set among a given set of entity types.

Degree of Relationship Type – It is the number of entity type participating.

**8. What is degree of a Relation? **

It is the number of attribute of its relation schema.

**9. Explain Multivalued dependency? **

Multivalued dependency denoted by X–>Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties

- t3[x] = t4[X] = t1[X] = t2[X]
- t3[Y] = t1[Y] and t4[Y] = t2[Y]
- t3[Z] = t2[Z] and t4[Z] = t1[Z]

where [Z = (R-(X U Y)) ]

**10. What is VDL (View Definition Language) explain? **

It specifies user views and their mappings to the conceptual schema.

**11. How does Tuple-oriented relational calculus differ from domain-oriented relational calculus? **

The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL

The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.