Database SQL Interview Questions

What is DBMS ?

The database management system is a collection of programs that enables user to store, retrieve, update and delete information from a database.

What is SQL ?

Structured Query Language(SQL) is a language designed specifically for communicating with databases. SQL is of ANSI (American National Standards Institute) standard.

What are the different types of SQL statements ?

This is one of the frequently asked SQL Interview Questions to freshers. SQL statements are broadly classified into three. They are as follows:

  1. DDL – Data Definition Language
    DDL is used to define the structure that holds the data. For example, Create, Alter, Drop and Truncate table.

  2. DML– Data Manipulation Language
    DML is used for manipulation of the data itself. Typical operations are Insert, Delete, Update and retrieving the data from the table. Select statement is considered as a limited version of DML, since it can't change data in the database. But it can perform operations on data retrieved from DBMS, before the results are returned to the calling function.

  3. DCL– Data Control Language
    DCL is used to control the visibility of data like granting database access, set privileges to create tables etc. Example - Grant and revoke gives permission to the user to access data in database.

What is RDBMS ?

Relational Database Management system (RDBMS) is a database management system (DBMS) that is based on the relational model. Data from relational database can be accessed or reassembled in many different ways without having to reorganize the database tables. Data from relational database can be accessed using an API, Structured Query Language (SQL).

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What is a field in a database ?

A field is an area within a record reserved for a specific piece of data. Examples: Employee Name, Employee ID etc.

What are the Advantages of SQL ?
  1. SQL is not a proprietary language used by specific database vendors. Almost every major DBMS supports SQL, so learning this one language will enable programmers to interact with any database like ORACLE, SQL ,MYSQL etc.

  2. SQL is easy to learn. The statements are all made up of descriptive English words and the number of statements are comparatively less.

  3. SQL is actually a very powerful language and by using its language elements you can perform very complex and sophisticated database operations.

What is a Record in a database ?

A record is the collection of values/fields of a specific entity say for instance an Employee, Salary etc.

What is a Table in a database ?

A table is a collection of records of a specific type. For example, employee table, salary table etc.