DBMS Interview Questions and Answers For Graduates Part-2
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 attributes 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.