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DBMS Technical Interview Questions and Answers For Graduates Part-2

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dbms-image11. What is DML (Data Manipulation Language)?

This language that enable user to access or manipulate data as organised  by appropriate data model. Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data. Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how  to get those data

12. What is DML Compiler?

It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

13. What is Query evaluation engine?

It executes low-level instruction generated by compiler.

14. What is Functional Dependency?

Functional Dependency is the starting point of normalization. Functional Dependency exists when a relation between two attributes allows you to uniquely determine the corresponding attribute’s value.

15. What is 1 NF (Normal Form)?

The first normal form or 1NF is the first and the simplest type of normalization that can be implemented in a database. The main aims of 1NF are to:

1. Eliminate duplicative columns from the same table.

2. Create separate tables for each group of related data and identify each row with a unique column (the primary key).

16. What is Fully Functional dependency?

A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.

17. What is 2NF?

A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

18. What is 3NF?

A relation is in third normal form if it is in Second Normal Form and there are no functional (transitive) dependencies between two (or more) non-primary key attributes.

19. What is BCNF (Boyce-Codd Normal Form)?

A table is in Boyce-Codd normal form (BCNF) if and only if it is in 3NF and every determinant is a candidate key.

20. What is 4NF?

Fourth normal form requires that a table be BCNF and contain no multi-valued dependencies.

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