Whether you use Python, PHP, C#, Java, etc. Everywhere uses SQL, and the majority of interviewers ask SQL interview questions in most technical interviews.

Depending on their experience and other factors, candidates will most likely be asked SQL basic interview questions to advanced level SQL interview questions for professionals with 5 years of experience. We’ve compiled a list of frequently asked SQL interview questions, organized by the needs of the individual.

Easy Navigation with TOC

Let’s start with SQL basic interview questions

Basic is important for beginners to experts. Let’s start with the SQL basic interview questions for freshers or experience.

Let's start with SQL basic interview questions
Start with ABC

1) What is SQL full form?

SQL stands for Structured Query Language.

2) What is an SQL database?

SQL (Structured Query Language) uses relational databases (RDSMS) for handling structured data. Here data is stored only in the tabular form of rows and columns.

3) What is in SQL server?

SQL Server is a relational database management system, or RDBMS made for storing and retrieving data requested by other software applications, developed by Microsoft which supports ANSI SQL, which is the standard SQL (Structured Query Language) language.

4) Difference between SQL and NoSQL?

SQL databases provide great benefits for transactional data whose structure doesn’t change frequently (or at all) and where data integrity is paramount. It’s also best for fast analytical queries. NoSQL databases provide much more flexibility and scalability, which lends itself to rapid development and iteration

5) What is SQL server vs SSMS?

SQL Server is a database engine for storing data and querying it whereas SQL Server Management Studio (SSMS) is a GUI-based management tool for working with SQL Server databases.

6) What is SQL RDBMS?

RDBMS stands for Relational Database Management System

7) What is SQL and how does it work?

SQL (Structured Query Language) uses relational databases (RDSMS) for handling structured data. At first SQL query is written & parsed, and then processed by a query optimizer then the query reaches the SQL server, where it compiles in three phases; Parsing, Binding, and Optimization, after that all possible permutations and combinations are generated to find the most accurate query within a reasonable time.

8) What is in SQL script?

A set of SQL commands is saved in a file as SQL scripts that contain one or more SQL statements that are used to create, edit, view, run, and delete script files.

9) What is a SQL relational database?

SQL is a relational database. A relational database is a type of database that stores store data in tables and are related to one another.

10) What is Database normalization?

SQL normalization is a database design technique by which data redundancy can be reduced by eliminating undesirable characteristics.

11) What is 3nf in SQL?

The third normal form (3NF) is a database schema that uses normalization principles to reduce duplication of data, avoid data anomalies, ensure referential integrity, and simplify data management.

12) What is in the SQL statement?

SQL has an IN condition (sometimes called the IN operator) for testing whether an expression matches any value in a list of values This IN statement is used as a replacement of multiple OR conditions in a SELECT, INSERT, UPDATE, or DELETE statement.

13) What are SQL keywords?

SQL keywords are reserved words in SQL that have some individual functions to perform in the database. For example: – ADD, SELECT,CREATE ,INSERT.

14) What is SQL operator?

There are some special words or characters used for performing tasks. for example- basic arithmetic operations or complex comparisons. You will find the SQL operator within the WHERE clause of an SQL statement.

15) What is a select query in SQL?

SQL is a Structured Query Language used by relational databases for storing data in tabular form. Relational Database Management Systems (RDMS) like MySQL, Oracle, Sybase, Postgres, and SQL Server use SQL as their standard database language.

SELECT CustomerName,City FROM Customers;
Top 140 SQL Interview Questions and Answers | 2022 1
Select query output

16) How many SQL server languages are there? / Types of SQL statements?

There are 4 types of language statements or commands in SQL Server.

  • DML (Data Manipulation Language)
  • DDL (Data Definition Language)
  • DCL (Data Control Language)
  • TCL (Transactional Control Language)

17) What is the SQL clause?

In SQL we have in-built functions in SQL called Clauses, to deal with data easily stored in the table by filtering and analyzing the data quickly

18) What is not like SQL?

NOT LIKE is an operator in SQL used to exclude those rows that match the criterion followed by the LIKE operator.

19) What is SQL like?

SQL LIKE is a SQL operator which is used in a WHERE clause to search for a specified pattern in a column.

SELECT * FROM students<br>WHERE StudentName LIKE 'a%';

20) What is SQL GROUP BY?

SQL GROUP BY is a SQL statement used to group the rows with the same values into the summary rows.

SELECT column1, column2
FROM table_name
WHERE [ conditions ]
GROUP BY column1, column2
ORDER BY column1, column2

21) What is SQL Union?

The Union operator in SQL combines the result of two or more SELECT statements where the SELECT statement within the Union operator should have the same number of columns and the columns should have similar data types and in the same order.

22) What are SQL constraints?

SQL constraints are the set of rules that are implemented on SQL databases. You can apply these constraints either on a column level or a table level. For

Example: – You can specify the limit on the type of data to be inserted, updated, or deleted in its tables.

23) What is SQL’s primary key?

The primary key is a UNIQUE field in SQL which uniquely identifies each record in a table, a table can have only one primary key, and cannot contain NULL values.

24) What is SQL foreign key?

A foreign key is a column in one table that refers to the primary key/unique key of another table. Foreign keys in SQL prevent actions that would destroy links between tables.

SQL Interview Questions for Experienced

We have completed the first milestone by going through the list of basic SQL interview questions and answers. Next is to get some expertise lever interview questions on SQL.

25) What is SQL procedure?

Procedures in SQL are the subprograms that we can create and save as database objects. It is also referred to as stored procedure. SQL procedure is a group of SQL statements and logic, that are compiled and stored together to perform some specific tasks.

26) What is SQL trigger?

In SQL, the trigger is a stored program in a database that automatically executes when an event in the database occurs. For example, a trigger can be executed when a row or column will be inserted or updated into a specified table.

27) What are SQL views and their usage?

In SQL view is the type of virtual table of rows and columns where predefined SQL query is stored like they were in a real table in the database.

28) What is an SQL transaction?

SQL transaction is a set of tasks performed against a database. If all the transaction is completed it results in success whereas if any of the tasks fail, the transaction fails.

29) What is an SQL execution plan?

An execution plan is a graphical representation of various steps that are involved in fetching results from the database tables in SQL Server Management Studio.

30) What is SQL query optimization?

Query optimization is a feature in SQL (other relational database management systems and graph databases also have this feature ) that tries to determine the best way to execute a given query by considering all the possible query plans.

31) What is SQL injection and how do you prevent it?

SQL Injection (SQLi) is a type of injection attack, where the attacker can inject and execute malicious SQL statements that will control a database server behind a web application.

If the attacker finds any SQL Injection vulnerabilities, then they can bypass application security measures. They can play around with the authentication and authorization of a web page and can also change the entire SQL database by adding, modifying, and deleting records in the database.

The best way to prevent SQLi is by sanitizing your code input validation and parameterized queries including prepared statements. You can do an Acunetix scan to find out any SQLi and prevent it.

32) what is SQL optimization?

SQL optimization is the process of choosing the best efficient way to execute the SQL queries to get accurate and fast database results. Some of the database queries are INSERT, SELECT, UPDATE, DELETE, and CALL which are coupled with subqueries to filter the results.

33) Can SQL store images?

Yes, SQL support image datatype.

34) What is SQL having a clause?

The SQL HAVING clause is used only in the SELECT statements as to where keywords cannot be used with aggregate functions to filter data based on defined criteria.

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;
Top 140 SQL Interview Questions and Answers | 2022 2
Select query output group by

3)What is SQL query tuning?

SQL query tuning is the fastest way to accelerate relation database performance.

36) What is the SQL window function?

A window function in SQL is used to perform calculations across a set of table rows that are anyhow related to the current row.

37) What is SQL transformation in Informatica?

SQL Transformation is a connected transformation for processing SQL queries in the midstream of a pipeline. By using SQL transformation, we can insert, update, delete and retrieve rows from the database at run time.

storage and provides many exciting features like integrating SQL Server relational databases with big data, and data virtualization.

38) How often does the SQL server update statistics?

SQL Server automatically updates the statistics every time after an index rebuild.

39) What is SQL mapping?

We can publish data service functions as SQL objects with the help of SQL Map, which is created when you specify the mapping, with the help of SQL Maps, we can expose data services modeled in Oracle Data Service Integrator as relational data sources.

40) Can SQL be used in excel?

Yes, Excel provides a wide range of features to import the data. One of them is to connect directly with the SQL server by using the SQL connection string.

41) what is SQL helper?

SQL Helper class is used in Data Access Layer for interacting with the database by taking the help of connection string provided, it also improves the performance for Business Layer & Data Access Layer. Some Methods are:-

  • ExecuteNonQuery
  • ExecuteDataset,
  • ExecuteDataTable
  • ExecuteReader,
  • ExcuteScalar & more

42) What is SQL/XML?

SQL/XML refers to the XML extensions of SQL, this XML is a data type that is used to store the unstructured or heterogeneous data in SQL Server.XML data type was used before JSON data type.

43) What is SQL outer join?

In SQL, the outer JOIN (left and right outer join ) will integrate all the content of both the tables together whether they are matched or not.

44) What is SQL’s high availability?

SQL High Availability means that the SQL Server database is very highly available and reachable in minimum possible downtime when there is any server crash or failure

45) What are SQL and PL-SQL?

SQL is a database Structured Query Language where Data variables are not available whereas PLSQL is a database programming language using SQL where Data variables are available.SQL a declarative language and PLSQL is a procedural language.

46) How often is SQL used? / is SQL obsolete?/will SQL die?/will SQL be replaced?

Although SQL is very old still it is one of the most often used standard data access languages even in 2021. And no SQL is not obsolete and not likely to be obsolete or replaced in the near future

47) Will ABAP be obsolete?

No.

48) What does SQL join and how many types are there?

A join clause in SQL is a query used to combine columns from one or more tables into a new table.

There are five types of JOIN:

  • INNER
  • LEFT OUTER
  • RIGHT OUTER
  • FULL OUTER
  • CROSS.

49) What is SQL order by?

We can use SQL ORDER BY clause to sort the fetched data of one or more columns in ascending or descending order. By default, ORDER BY sorts the data in ascending order.

For sorting it in descending order we can use the DESC keyword like this: –

SELECT * FROM table_name ORDER BY column1 ASC|DESC , column2 ASC|DESC

50) What is SQL rowcount in oracle?

SQL%ROWCOUNT attribute gives the value of the most recently executed SQL statement from PL/SQL to save an attribute value for later use by immediately assigning it to a local variable.

51) What is SQL where clause?

WHERE clause in SQL is a keyword for filtering data by giving a condition according to which data will be fetched by matching the given pattern.

SELECT * FROM Customers
WHERE Country='Mexico';
Output of select SQL query with where clause
Output of select SQL query with where clause

52) What is SQL mode?

SQL_mode in MySQL allows configuring certain parts of how the server executes SQL statements.

53) What is the wildcard character in an SQL-like statement?

For substituting one or more characters enabling is used with the LIKE operator of SQL. The 2 wildcard characters are The percent sign (%) and The underscore (_)

54) What is SQL merge?

In SQL a combination of three SQL statements: INSERT, UPDATE, and DELETE gives rise to the MERGE statement. there will be a source table that will be merged with the target table and all the mentioned 3 statements(INSERT, UPDATE and DELETE ) will be performed at once

55) What is an SQL developer job?

The SQL developer has to design, create and maintain databases and they also need to design database tables and structures.

56) What is SQL bulk copy?

With SQLBulkCopy we can write managed code solutions

57) Is it possible to connect SQL developer connect to PostgreSQL?

Yes, Oracle SQL Developer 4.0. 1.1 supports connections to PostgreSQL.

58) what is xa transactions SQL server?

An XA transaction is a global transaction that covers multiple resources.

59) what is xor SQL?

XOR is s SQL operator that will check 2 operands (or expressions) and returns TRUE if one of them is TRUE but not both is TRUE

60) What is SQL key?

An SQL key is a single column or a group of columns that identifies unique rows (or tuples) in a table. It makes sure that there are no rows with duplicate information.

61) What is SQL native client used for?

SQL Server Native Client can be used for creating applications or enhancing existing applications by taking the advantage of features such as multiple active result sets (MARS), user-defined data types (UDT), and XML data type support.

62) What is in SQL server data tools?

SQL Server Data Tools (SSDT) is a modern development tool used for building SQL Server relational databases

63) What is an SQL object?

SQL objects are schemas, journals, catalogs, tables, aliases, views, indexes, constraints, etc. These objects are created and maintained as system objects by SQL.

64) What is an SQL worksheet?

We can enter, edit, and execute SQL and PL/SQL code with the help of SQL Worksheet, and also you can run scripts from the SQL worksheet.

65) What is SQL key lookup?

When there is a use of a nonclustered index (although additional data is needed from the clustered index) to satisfy all or some of a query’s predicates by SQL that is when SQL key lookup occurs

66) What is oracle 11g?

This Oracle Database 11g is designed for teaching the fundamentals of SQL using Oracle Database 11g database technology.

67) What is SQL database in android?

There is an open source SQL database called SQLite, with the help of SQLite you can use SQL in android as SQLite comes inbuilt into android

68) What is SQLyog community?

SQLyog is a GUI tool used to manage the MySQL and MariaDB servers and databases in any type of physical, virtual, or cloud environment.

69) What is PostgreSQL?

PostgreSQL is an advanced version of SQL that has different functions of SQL such as foreign keys, subqueries, triggers, and different user-defined types and functions.

70) What is SQL go?

Go is a command that is recognized by the SQLcmd and SQL utilities and SQL Server Management Studio Code editor which is used to group SQL commands into batches and then sent to the server together.

71) What is SQLZoo?

SQLZoo is an online platform for writing and running SQL queries against a live database.

72) What is SQLYog?

SQLYog is a GUI tool for the RDBMS MySQL, which is by Webyog, Inc. It provides powerful means to manage your MySQL databases.

73) What is SQLyog used for?

SQLyog is a powerful MySQL development and administration solution that provides tools that enable database developers, administrators, and architects to visually compare, optimize, and document schemas.

74) What is SQL GUI?

Retool is a GUI tool that provides a graphical user interface to SQL.

75) What is SQL android?

SQL Android allows you to manage databases, edit tables, edit data, and execute queries and the basic functionality is free to use.

76) What is SQL used for in web development?

In web development different types of databases such as PostgreSQL, MySQL, SQLite. uses SQL as their database query language.

77) What is MySQL?

MYSQL is an open-source relational database management system (RDBMS) that is based on structured query language (SQL).

78) What is MySQL vs SQL server?

MS SQL Server is Developed by Microsoft and is not free whereas MySQL is Developed by Oracle and is open source.

79) What is SQL hive?

SQL developers write Hive Query Language (HQL) statements similar to standard SQL statements with the help of HIVE for data query and analysis.

80) What is SQLalchemy?

SQLAlchemy is an open-source SQL toolkit and object-relational mapper for the Python programming language which enables flexibility for the application developer to perform all types of tasks.

81) What is SQL browser service used for?

The function of SQL Server Browser is to listen to incoming requests for Microsoft SQL Server resources and inform about SQL Server instances that are installed on the computer.

For example: – Browsing a list of available servers. Connecting to the correct server instance.

82) What is an SQL cluster?

CLUSTER in SQL stores data from different tables inside the same physical data blocks.

83) What is SQL reporting

SQL reporting is a Server Reporting Services (SSRS) which is a server-based report-generating software system from Microsoft. It can be used to prepare and deliver a variety of interactive and printed reports.

84) What is SQL 92?

The SQL-92 was actually the third revision of the SQL database query language.

85) what is SQL3?

SQL3 or SQL 1999 was the fourth revision of the SQL database query language that comes with many new features and provides data definition and management techniques from Object-Oriented DBMS while maintaining the relational DBMS platform.

86) What is SQL server 2000?

SQL Server 2000 supports multiple instances of SQL Server to run on the same systems that allow you to simultaneously run one instance of SQL Server 6.5 or 7.0 along with one or more instances of SQL Server 2000.

87) What is SQL server version 8?

SQL Server Version 8 is SQL Server 2000.

88) What is SQL Server 2005?

SQL Server 2005 is the best option for using it in shared and dedicated Web hosting environments.

89) What is SQL 2008?

The sixth revision of the ISO and ANSI standard for the SQL database query language was adopted in July 2008 which was called SQL 2008. According to Microsoft, SQL Server 2008 Enterprise is a comprehensive data management and business intelligence platform for providing scalability, data warehousing, security, advanced analytics, and reporting support for running business-critical applications.

90) What is SQL server 2008 r2?

SQL Server 2008 R2 is a free edition of SQL Server used for learning, developing, powering desktop, web & small server applications.

91) What is SQL version 869?

The SQL Server 2017 has Internal Database Version 869.

92) How much is SQL server 2016 enterprise edition?

SQL 2016 Enterprise 2-pack of Core Licenses costs $14,256 ($7,128 per core) Per License.

93) What is SQL 2019?

The most current version of Microsoft SQL Server was released on 4 November 2019 which is designed to solve the challenges of modern data.

94) What is SQL anywhere 17?

SQL Anywhere 17 is a comprehensive package providing technologies such as data management and data exchange technologies that help in the development of database-powered applications for server, desktop, mobile, and remote office environments.

95) What is SQL RTM?

RTM stands for “release to manufacture

96) What is a SQL developer tool?

SQL Developer is a free GUI-based tool provided by Oracle that offers lots of options and facilities to simplify the development and management of the Oracle Database.

97) What is SQL database in Microsoft Azure?

Microsoft Azure SQL Database is a managed cloud database (PaaS) provided as part of Microsoft Azure.

98) What is SQL managed instance?

SQL managed instance is actually Azure SQL Managed Instance which is an intelligent and scalable cloud database service for combining the broadest SQL Server database engine compatibility with a fully managed and evergreen platform as a service.

99) What is SQL on demand?

SQL on-demand is a serverless query service by which we can run SQL queries on files placed in Azure Storage.

100) What is SQL pool in azure?

SQL Pool was formerly known as Azure SQL Data Warehouse which is the traditional Data Warehouse for managing and scaling multiple databases with unpredictable usage demands. It is a Big Data Solution for storing data in a relational table format using SQL.

101) what is SQL Bacpac?

A ZIP file with an extension of BACPAC having the metadata and other data from the database is called a BACPAC file, this file can be stored in Azure Blob storage.

102) What is SQL elastic pool?

SQL elastic pools are Azure SQL Database elastic pools that are budget-friendly solutions for managing multiple databases with changing and unpredictable usage demands.

103) What is SQL API in cosmos DB?

The SQL API lets the Azure Cosmos DB support querying documents using SQL.

104) What is an SQL exception? / what is SQL exception in java?

SQL exception gives the information on a database access error or other errors.

105) What is an SQL grammar exception?

The SQLGrammarException occurs when the SQL query generated has the wrong SQL syntax or is invalid.

106) what is an SQL keyword error?

SQL keyword errors occur when one of the reserved words in the SQL query language is misspelled.

107) What is SQL error 18456?

The message “Login Failed for User (Microsoft SQL Server, Error: 18456)” is a SQL error that occurs when the user enters invalid credentials while logging into SQL Server.

108) What is SQL error 42601?

In SQL, the error 42601 occurs when there is any Syntax Error or Access Rule Violation.

109) What is 0 in SQL?/what is SQL error code 0/what is SQL null?

In SQL “0” indicates a special value, called the null value which means Absence of Data. It simply shows that there is no data value at a particular place but why it is not there is not mentioned.

110) What is msg 8152 in SQL?

This error message 8152 is a SQL error that occurs while inserting a record in a table, it occurs If one of the columns is a VARCHAR or CHAR data type when the length of the value that is inserted is longer than the length of the column.

111) What is SQL state 42601?

The error SQL state 42601 is a “Syntax Error or Access Rule Violation“that occurs due to the syntax errors in the queries executed.

112) What is SQL server error 53?

SQL server error 53 is a network-related or instance-specific error, this arrow is thrown when there is a problem in establishing a connection to SQL Server.

113) What is SQL state 08001?

This is an error that occurs when SQL StateServer Connection fails while creating an ODBC connection on Microsoft SQL

114) What is SQL code 913?

The SQL error that shows the code -913, is an error caused due to UNSUCCESSFUL EXECUTION CAUSED BY DEADLOCK OR TIMEOUT.

115) What is SQL handled in SQL server?

A hash of the SQL text having comments, white space, different casing, etc and is unique for each batch is called SQL handle

116) what is SQL code 904?

It is an error code that occurs when execution is unsuccessful due to unavailable resources

117) What is error 40 in SQL server connection?

When you fail to connect to the server instance that we are using then the server throws an Error: 40

SQL DBA interview questions

Interview questions and answers for SQL database administrator or DBA.

118) what is SQL VDI?

SQL VDI is an API used for communicating with a SQL Server during all backup and restore operations.

119) How often are SQL patches released?

It releases the Cumulative Packs every 2 months.

120) What is SQL port 1433?

By default, Port 1433 is the port for TCP that is needed to connect to the SQL database instance.

121) Maximum CPU used by SQL server?

SQL server will utilize a maximum of 4 CPUs at the same time

122) Can SQL server run on Linux?

Yes, from SQL Server 2017, SQL Server can run on Linux

123) What is SQL native client?

SQL Server Native Client is actually a stand-alone data access application programming interface (API) used for OLE DB and ODBC.

124) What is SQL replication?

SQL replication is a type of replication that is used for copying and distributing database objects from one database to another and also synchronizing between databases to maintain consistency and integrity of the data.

125) 7) What is SQL management studio?

SQL Server Management Studio (SSMS) is a software application first launched with Microsoft SQL Server 2005 for configuring, managing, and administering all components within Microsoft SQL Server.

126) How many SQL licenses do I need?

at least four core licenses for each physical processor on the server

127) 6) What is a SQL file?

SQL Files contain the. SQL file extension which holds database-related files written in the SQL language. An SQL file holds the code for modifying the contents of an associated database. For example:- statements to create or modify the structure of the database.

128) 8) What is SQL workbench used for?

The SQL workbench is used for the following reason: –

  1. data modeling
  2. SQL development
  3. user administration

129) What is SQL loader?

SQL*Loader loads data into tables from external files of an Oracle database. You can use SQL*Loader Load data across a network.

130) What is SQL hosting?

SQL Hosting is an online hosting service that uses the SQL language to provide a database backend for your website to store and retrieve data from a database.

For example- Oracle, MySQL, and MS Access are some common SQL hosting databases.

131) What is SQL loader in oracle?

SQL*Loader is used to load the data from external files into tables of an Oracle database. SQL *loader has powerful data parsing engine to put limitations on the format of the data in the data file.

132) How often should the SQL server be rebooted?

It is recommended to reboot the SQL server at least once per month

133) what is SQL server agent XPS?

The SQL Server Agent XPs are extended stored procedures that provide privileged actions that run externally to the DBMS which are used by the SQL Server Agent under the security context of the SQL Server Agent service account.

134) What is SQL server XTP?

The SQL Server XTP contains n-Memory OLTP database-specific counters that are related to transactions involving In-Memory OLTP in SQL Server.

135) Can SQL server run on mac?

Yes. you can directly install an SQL server on a mac without the need for a virtual machine.

136) What is SQL gateway?

The SQL Gateway is an application to get remote access to ODBC data sources as if they were MySQL or SQL Server databases.

137) What are SQL job scheduler tasks?

A job scheduler task in SQL server means pre-scheduling a job in SQL server and then running it automatically at given scheduled time intervals by the job scheduler.

138) What is SQL ODBC driver?

Open Database Connectivity (ODBC) is a standard application programming interface (API) for accessing database management systems (DBMS). This ODBC driver uses the ODBC interface by Microsoft so that the applications can access data in database management systems (DBMS) with the help of SQL as a query language for accessing the data.

139) What is SQL backup?

SQL backup means copying the SQL Server database to some other backup device, such as a disk so that the backup data can be used later on to restore and recover the original data in case of any failure.

What is SQL injection and how do you prevent it?

SQL Injection (SQLi) is a type of injection attack, where the attacker can inject and execute malicious SQL statements that will control a database server behind a web application.

Can SQL be used in excel?

Yes, Excel provides a wide range of features to import the data. One of them is to connect directly with the SQL server by using the SQL connection string.

What is XA transactions SQL server?

An XA transaction is a global transaction that covers multiple resources.

What is SQL go?

Go is a command that is recognized by the SQLcmd and SQL utilities and SQL Server Management Studio Code editor which is used to group SQL commands into batches and then sent to the server together.

What is SQLalchemy?

SQLAlchemy is an open-source SQL toolkit and object-relational mapper for the Python programming language which enables flexibility for the application developer to perform all types of tasks.

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