DBMS Interview Questions and Answers

The E-R model stands for the Entity Relational Model. The E-r model is a way of representing the logical relationship between the entities or the objects in order to create a database. The ER model was developed by Peter Pin-Shan Chen in the 1970s.

A single query can be solved or executes by writing different query plans or algorithms. Query optimization is a process in which the query optimizer chooses the most efficient algorithm to perform the given query.

The denormalization is an optimization process to increase the data redundancy in the database. As a result, the joins are avoided, and the performance of the database structure is improved. Denormalization is done after the normalization process.

Database systems are the multilayered system. Data independence refers to altering the data of one layer without the on other layers.

There are two types of Data Independence:-

• Logical Data Independence:-Logical schema is modified without rewriting the application programs.
• Physical Data Independence:- Physical schema is modified without rewriting the application programs.

The database index is the data structure that is defined on the columns of the database table. Database indexing speed up the data retrieval process.

There are 3 types of indexing in DBMS:-

• Primary Index
• Secondary index
• Clustered index

DML stands for Data Manipulation Language.DML compiler translates the DML statements which are there in a query language into the low-level instructions which the query evaluation engine understands easily.

When many transactions are executed at the same time, then the logs are interleaved. As a result, it becomes tough for the recovery system to recover the data.

Checkpoint acts as a bookmark that makes the inspections during the transaction execution. Each checkpoint, the previous logs are removed from the system and are stored in the storage disk. As a result recovery of the data is faster.