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SQL, also called sequel, is a language used to pull, edit, manipulate, and update data from databases. SQL works with relational databases that have a tabular schema, and it creates, joins, and alters tables as a response to queries. Online businesses store their data online and use the structured query language to communicate with the databases. SQL’s use is prominent across industries such as sales, marketing, and in a wide range of tech-related jobs. 

Companies with an online presence use databases and hire professionals who can work with the data. If you are looking to hire SQL candidates for entry-level or experienced proficiencies, make sure to include the below-listed SQL Interview Questions in your recruitment process. A candidate’s response to these questions can reveal their knowledge of the SQL language.

Basic questions to ask in SQL interviews

Are you preparing for a SQL interview and wondering about the different types of basic SQL interview questions you should ask?

Listed below are a few of the most commonly asked questions in your SQL interviews.

  1. What are tables and fields in the database?
  2. What are the subsets of SQL?
  3. What is the difference between a primary key and a unique key?
  4. What do you mean by DBMS? What are its different types?
  5. What are Constraints?
  6. What are Tables and Fields?
  7. What is a Primary Key?
  8. What is a Unique key?
  9. What is the difference between DELETE and TRUNCATE statements?
  10. What is normalization and its types?
  11. What are the applications of SQL?
  12. Explain Inner Join with an example?
  13. Explain the types of SQL joins?
  14. What is a UNIQUE constraint?
  15. What are the applications of SQL?
  16. What is a Query?
  17. What is the SELECT statement?
  18. What are UNION, MINUS and INTERSECT commands?
  19. What are Entities and Relationships?
  20. What is an Alias in SQL?

SQL Interview Questions and Answers

1. What can be used to add a row in a database using SQL?

  1. ADD
  2. AUGMENT
  3. INSERT
  4. CREATE

Ans: C

2. What command will you use to remove rows from a table 'AGE'?

  1. REMOVE FROM AGE 
  2. DROP FROM AGE 
  3. DELETE FROM AGE WHERE 
  4. UPDATE FROM AGE 

Ans: C

3. What does the SQL WHERE clause do?

  1. Limits the column data that are returned
  2. Limits the row data that are returned
  3. Both a and b
  4. None of the above

Ans: B

4. What is the purpose of SQL?

  1. To define data structures
  2. To specify the syntax of DDL
  3. To specify the syntax of DML
  4. All of the above

Ans: D

5. The wildcard in a WHERE clause is used when___________

  1. A right match is required in a SELECT statement
  2. A right match is possible in a CREATE statement
  3. A right match is not possible in a SELECT statement
  4. None of the above

Ans: C

6. Define a view?

  1. A virtual table that can be accessed with SQL commands
  2. A base table that can be accessed with SQL commands
  3. Both a and b
  4. None of the above

Ans: a

7. What command will you use to eliminate a table from a database?

  1. ELIMINATE TABLE CUSTOMER;
  2. DROP TABLE CUSTOMER;
  3. DELETE TABLE CUSTOMER;
  4. APPRISE TABLE CUSTOMER;

Ans: b

8. What does an ON UPDATE CASCADE ensure?

  1. Standardization
  2. Data Integrity
  3. Both a and b
  4. None of the above

Ans: B

9. What does SQL data definition commands make up?

  1. DDL
  2. DML
  3. DQL
  4. DCL

Ans: A

10. Choose the valid SQL for an Index?

  1. CREATE INDEX ID;
  2. ALTER INDEX ID;
  3. ADD INDEX ID;
  4. DELETE INDEX ID;

Ans: A

11. Which SQL keyword(s) is used with wildcards?

  1. IN and NOT IN
  2. NOT IN only
  3. LIKE only
  4. IN only

Ans: C

12. Choose the correct order of keywords for SQL SELECT statements

  1. WHERE, SELECT, FROM
  2. SELECT, FROM, WHERE
  3. SELECT, WHERE, FROM
  4. FROM, WHERE, SELECT

Ans: b

13. What is a subquery in an SQL SELECT statement enclosed in?

  1. brackets []
  2. braces {}
  3. parenthesis () 
  4. none of the above

Ans: C

14. What is the result of a SQL SELECT statement?

  1. report
  2. form
  3. table
  4. file

Ans: c

15. Select the built-in functions provided by SQL

  1. SUM, MIN, MAX, MULT, AVG
  2. SUM, MULT, DIV, MIN, AVG
  3. SUM, MIN, MAX, NAME, AVG
  4. COUNT, SUM, AVG, MAX, MIN

Ans: D

16. What is the full form of SQL

  1. Structured Query Language
  2. Structured Query List
  3. Simple Query Language
  4. None of these

Ans: A

17. Which of the below is not a valid SQL type?

  1. FLOAT
  2. NUMERIC
  3. DECIMAL
  4. CHARACTER

Ans: C

18. Which statement is used to delete all rows in a table without having the action logged?

  1. DELETE
  2. REMOVE
  3. DROP
  4. TRUNCATE

Ans: D

19. Which of the below should be enclosed in double quotes?

  1. Dates
  2. Column Alias
  3. Strings
  4. All of the above

Ans: B

20. SQL Views are also known as

  1. Simple tables
  2. Virtual tables
  3. Complex tables
  4. Actual Tables

Ans: D

21. Which of the below is not a valid aggregate function?

  1. COUNT
  2. COMPUTE
  3. SUM
  4. MAX

Ans: B

22. SQL is

  1. a programming language
  2. an operating system
  3. a data sublanguage
  4. a DBMS

Ans: C

23. Which SQL statement is used to update data in a database?

  1. SAVE
  2. UPDATE
  3. SAVE AS
  4. MODIFY

Ans: B

23. Which statement is true regarding routines and triggers?

  1. Both consist of procedural code.
  2. Both run automatically.
  3. Both are stored in the database.
  4. Both have to be called to operate.

Ans: A

24. Sequence can generate

  1. Numeric value
  2. Alphanumeric value
  3. A & B both
  4. None of the above

Ans: C

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Online Assessments for Assessing Programmers

An online test can be used to measure different types of technical skills. You can make use of an online test platform to administer multiple-choice SQL query interview questions in the pre-hiring stage. If the job role requires an assessment of coding abilities, then you can make use of the online coding tests to analyse simple to complex coding skills. You can assess different levels of coding proficiencies required for job roles

across industries using online assessments. You also have the option to measure specific programming skill sets by using project-based coding questions or customised domain-specific questions. The online tests are automated to ensure a quick turnaround of results.

Applications of MeritTrac Assessment Solutions

Assessing technical skills through traditional recruitment methods can be quite challenging. If you are a recruiter from a non-IT background, then MeritTrac’s assessment platforms can help you administer technical tests with ease. You can evaluate various levels of SQL proficiencies with MeritTrac’s online assessment platforms. These platforms come with an auto evaluation feature that provides quick test results and helps you select efficient candidates in less time. Its comprehensive reports let you evaluate the code’s simplicity, readability, and other parameters. 

MeritTrac’s online test platforms offer a plethora of features that simplify technical hiring. Recruiters can administer these online tests to candidates in any location. They can also remotely monitor the tests, assess the results, and make hiring decisions on the spot. 

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MeritTrac’s scientifically designed assessment solutions feature regularly updated SQL interview questions and customisable coding scenarios. Online tests administered through MeritTrac platforms can help to cut down on cost, time, and effort involved in your hiring process.

SQL Interview Questions

1. What is SQL?

SQL stands for Structured Query Language, is the standard language for dealing with relational databases. SQL can be used to insert, search, update, and delete database records. SQL can do many other operations, including optimizing and maintaining databases.

2. What is Database?

A database is an organised collection of data stored and retrieved digitally from a remote. The database is also known as a structured form of data that can be accessed in multiple ways.

3. What is a database management system (DBMS)?

Database management system is a software which is used to manage the database. MySQL, Oracle, etc are a very popular commercial database which is used in different applications. DBMS provides an interface to perform various operations like database creation, storing data in it, updating data, creating a table in the database and a lot more.

4. What are the subsets of SQL?

Data definition language (DDL)
Data manipulation language (DML)
Data control language (DCL)
Transaction Control Language (TCL)

5. What is a Query in SQL?

A query is a question or inquiry about a set of data. We use Structured Query Language (SQL) to retrieve meaningful and relevant information from databases. When building a structure, we pull data from tables and fields. The fields are columns in the database table, while the actual data makes up the rows.

6. What is a unique key?

A unique key is a single (or) combination of fields that provide all the values stored in the column that will be unique. It means a column cannot store duplicate values. This key ensures uniqueness for the column or set of columns. For example, the email ID and roll numbers of students' tables must be unique. It can allow the null value but only one null value per column. It provides the integrity of the column or group of columns to store different values in a table.

7. What is RDBMS?

RDBMS stands for Relational Database Management System. RDBMS stores data in the form of a group of tables and relations can be specified between the common fields of these tables. Most modern database management systems like MySQL, Oracle, Microsoft SQL Server, IBM DB2, and Amazon Redshift are based on RDBMS.

8. What are some common clauses used with SELECT queries in SQL?

The following are some examples of SQL clauses that are commonly used with a SELECT query:

  • In SQL, the WHERE clause is used to filter records based on certain criteria.
  • The ORDER BY clause in SQL is used to sort data in ascending (ASC) or descending (DESC) order depending on a specific field(s) (DESC).
  • The SQL GROUP BY clause is used to group entries with identical data and can be combined with aggregation procedures to provide summarised database results.
  • In SQL, the HAVING clause is used in conjunction with the GROUP BY clause to filter records. It differs from the WHERE clause in that it cannot filter aggregated records.

9. What is the primary use of Normalization?

Normalization is most commonly used to add, delete, or edit a field in a single table. Normalization is mostly used to eliminate redundancy as well as insert, delete, and update distractions. To avoid repetition, normalization divides the table into small segments, which are subsequently linked using different relationships.

10. What is the difference between DROP and TRUNCATE statements?

When a table is removed, everything linked with it is removed as well. This comprises the table's associations with other tables, as well as the table's integrity checks and restrictions, access privileges, and other grants. All of these relations, checks, limitations, privileges, and associations must be redefined in order to recreate and use the table in its original form. When a table is truncated, however, none of the aforementioned issues arise, and the table preserves its original structure.

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