SQL is probably used for database interaction and management. Nowadays, SQL skills are essential for getting jobs, especially in the web development field.

In this blog, I am going to introduce a set of SQL interview questions to cope up with the growing competition in IT markets.





Let's Continue !!



1) What is DBMS?

DBMS is known as the file manager program that is designed for data management in the database which includes creating, implementing, and maintaining data.

It provides a systematic method to perform modification, administration, and retrieval. Data present in the DBMS's applications are stored as a file.

2) What is RDBMS?

3) What do you mean by SQL?

4) What do you mean by "Table" in a Database?

5) What is "Record" in a Database?

A relational database management system (RDBMS) is a software program store information in the form of tables. Moreover, it offers the relational operators for performing data manipulations across the tables.SQL (Structured Query Language) is known as the standard language to interact with the database. It is designed to accomplish database tasks like retrieval and insertion.A table is known as a database object that can be used for storing the record in terms of rows and columns.A record is known as the row of the table that contains arranged sets of interrelated data. It has the capability to hold multiple values. Moreover, It is known as a data structure to hold different kinds of data items.

Example

<402 yuvi 405>



6) What do you mean by the "database" in DBMS?

7) List some major objectives of DBS?

Data availability

Data integrity

Data independence

8) List some applications of the DBS system?

Reservations systems

Telecommunications

Banking

Sales

Scientific applications

9) What are the keys that are present in DBMS?

Candidate key

Foreign key

Primary key

Secondary key / Alternate key

Composite key

Super key

10) How can you maintain and identify relations between two or more than two tables in DBMS?

11) Discuss the role of keys in DBMS?

Impose Integrity

Uniquely identify the records within the table

Identify and maintain relations between tables

To fetch the records from a database

12) What is the need of the "keys" in an organization?

The database comprises of logically related records or data.There are mainly six key founds in DBMS to manage the table. They are:Keys are used in maintaining the relationship between tables.Keys are referred to as the set of one or more attributes that are used for unique identification. They are used to provide the record's uniqueness.

Use-case

For instance, suppose you want to store the huge amount of unformatted data of an organization. Keys are implemented along with conditions to fetch any specific record from that organization.

Thus keys in the database are used to avoid duplicities and to streamline record's identification.



13) What is the role of "Database Testing" in SQL?

Database testing is one of the most considerable testing techniques. This scheme needs a tester with an expert to investigate tables, procedures, and written queries. Through the back-end data, the integrity of front-end data is verified.

Although, it validates the database tables, triggers, junk records, and performs record modification. Database testing can be used in the applications of Oracle or SQL.

Application of Database Testing :

Banking project

Finance

All health insurance-related projects in which extensive database testing is required.

14) What is the difference between DELETE and TRUNCATE command?

Delete Command is used to delete a row in a table whereas the truncate command is used to delete entire rows. Delete command is slower as compared to truncate statement.

You cannot rollback data after applying the truncate command.



15) "If anyone wants to calculate values from multiple columns in a table" which type of functions can be used in SQL?

16) What do you mean by "Aggregate functions" in SQL?

17) Name the Aggregate functions that are found in SQL?

COUNT

MAX

MIN

FIRST

LAST

SUM

AVG

We can use "Aggregate functions" to calculate the values of multiple columns in a table.Aggregate functions are used to perform calculations on multiple columns and rows in a table. As a result, they return a single value. Also, these Aggregate functions allow you to produce the report of summarized data effortlessly.There are seven Aggregate functions used in SQL i.e.

MIN(): To returns the smallest value among records

MAX(): To returns the largest value from specified columns



SUM(): To returns the sum of the numeric values of specified

AVG(): To returns the average value of a particular column

COUNT(): To returns the entire number of values in a given column



FIRST(): To Returns the initial value of the record

LAST(): To Returns the finishing value of the given records



18) Name some leading Database management systems used in MNC?

MySQL

PostgreSQL

MongoDB

Microsoft Access

Microsoft SQL Server

Oracle

DB2

Sybase

19) What is the different type of statement in SQL?

DDL - Data Definition Language

DQL - Data Query Language

TCL - Transaction Control Language

DML - Data Manipulation Language

DCL - Data Control Language

20) Triggers in SQL

SQL Statements can be separated into the following types:Triggers are identical to the procedures that are stored to bring a response of a specific action applied on a table. A specific action may be an insertion, deletion, or update. Triggers can also be invoked explicitly. The main components of SQL triggers are action and event.

Syntax :

CREATE TRIGGER name {BEFORE|AFTER} (event [OR..]}

ON table_name [FOR [EACH] {ROW|STATEMENT}]

EXECUTE PROCEDURE function name {arguments}



21) List some operations of Data Manipulation Language?

Insertion of data into the database

Retrieval of data from the database

Updation and deletion of data in the database

22) Name the commands of the Data control language?

GRANT is used to grant specific task to a user

REVOKE is used to repeal or cancel user access

DENY is used to deny the permission

23) Can we Rollback data in a database, which has been committed with a commit keyword?

24) What is the different type of TCL commands used in SQL?

We can control the access of the database with the use of the commands i.e. GRANT, DENY and REVOKE.NoThe modifications done by DML statements can be managed through the TCL commands i.e. COMMIT, SAVEPOINT, and ROLLBACK. These commands are used in transaction management

Commit: Commit is used to save changes permanently.

Syntax: COMMIT;

Rollback: Rollback command is used to restore or undo the work done in the current transaction.

Syntax : ROLLBACK TO savepoint-name;

Savepoint: This transaction command is used to save a transaction temporarily for further rollback requirements.

Syntax : SAVEPOINT savepoint_name;



25) What is the role of SQL Alias?

Alias is the process of giving a temporary name to a table or column. Moreover, it is applicable in the case of large or complex queries.

Following is the syntax for SQL Alias for tables name:

SELECT column-name FROM table-name AS alias-name



26) What do you mean by the DISTINCT Keyword in SQL?

The Distinct keyword is used along with SELECT Statement to eliminate the duplication at the time of retrieving particular records from the table.

Syntax :

SELECT DISTINCT column-name FROM table-name;



27) What do you mean by Order by clause?

Order by clause is used with a select statement for organizing retrieved data in sorted order i.e. ascending or descending order.

Syntax :

SELECT column-list|* FROM table-name ORDER BY DESC | ASC



28) What is the minimum condition required for joining the table in SQL?

29) What is the main difference between Alias and Rename?

30) What do you mean by JOIN?

(n-1) where n, is a number of tables.Alias is the temporary name given to any table whereas 'Rename' is the permanently given name to any column or table.

Joins are used for combining rows from two or more than two tables. There are four types of joins that are available in SQL. They are INNER JOIN, RIGHT JOIN, LEFT JOIN, and OUTER JOIN.