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Top 10 Questions And Answers For A SQL Interview

The following is a list of the most prominent and helpful SQL interview questions and answers for applicants who are either new to the field or have previous experience.
These questions have been developed with the express purpose of acquainting you with the kinds of questions that you could be asked during your SQL interview.
During the interview, excellent interviewers rarely intend to ask questions on any particular subject, as our experiences have shown us. T
on the other hand, the questioning process often starts with a fundamental comprehension of the topic, and further conversation is dependent on your replies.
Top 10 SQL Interview’s Questions And Answers
- What exactly is SQL?
Structured Query Language is what SQL is an abbreviation for. The programming language is generally accepted to maintain the relational database and carry out a wide variety of data manipulation operations on the data.
In 1970, SQL was first developed and implemented. It is a database language that may be used to create databases, delete databases, retrieve and alter rows, and perform other similar operations.
Additionally, it is sometimes pronounced as “sequel.” Furthermore, we can use it for the management of structured data that is composed of entities (variables) and relations between the many entities that make up the data.
- When was SQL first introduced?
SQL made its debut in 1974.
When it comes to maintaining relational databases, it is one of the languages used the most. ANSI, which stands for the American National Standards Institute, adopted SQL as its standard in 1986, and ISO, which stands for the International Organization for Standardization, adopted it in 1987.
- What are some of the applications of SQL?
SQL, which is in charge of their maintenance, looks after the database’s relational data and data structures. Following is a list of some of the most common applications:
- To run queries against a database
- If you want to obtain data from a database
- To add entries to a database by inserting them
- If you want to update records in a database
- The process of removing entries from a database
- To establish brand new databases
- In a database, the process of creating new tables
- When a database is used to construct views to carry out tasks that are difficult on the database.
- Is SQL capable of supporting the characteristics of programming languages?
The Standard Query Language is often referred to as SQL. As a result, it is correct to say that SQL is a language; nevertheless, it does not truly support the programming language.
A loop, conditional expressions, and logical operations are not included in this language, which is a common language. It is not possible to utilize it for anything other than manipulating data.
https://youtu.be/aGGJLDgIrD8?si=S9ngrr45H15mZsr5
For the purpose of carrying out database operations, it is a command language. SQL is primarily used to access, alter, update, and remove data from a database and execute complicated operations such as joins on the data already there in the database.
- When it comes to SQL, what are the subsets?
This is a list of the four important subsets that are included in the SQL:
- Data description language, often known as DDL, is a language that is used to specify the data structure. It includes commands such as CREATE, ALTER, DROP, and others.
- The term “data manipulation language” (DML) refers to a language that manages the data already in a database. SELECT, UPDATE, INSERT, and similar instructions fall under this group of commands.
The data control language, or DCL, controls who can access the database’s information. GRANT and REVOKE are two examples of commands that fall within this category. - Transaction Control Language (TCL) is a language that is used for the purpose of managing the transactions that take place inside the database. The instructions under this category are SET TRANSACTION, SAVEPOINT, ROLLBACK, and COMMIT, among others.
- What aims does the DDL language seek to accomplish?
The abbreviation for “data definition language” is “DDL.” At the time when a database is being built, the subset of the database is responsible for defining the data structure of the database. Adding, removing, or modifying tables is one example of what we may do using the DDL commands. The following commands are included in it: Create, alter, and delete database objects. These include schema, tables, indexes, views, sequences, and other similar items.
Example: CONSTRUCT A TABLE
Students (Roll no INT, Name VARCHAR(45), Branch VARCHAR(30), );
- In what way does the DML Language serve its purpose?
The ability to obtain and modify data stored in a relational database is available to the user via data manipulation language. Concerning data, the DML commands are only capable of performing read-only actions.
With the help of the DDL language, we can carry out the following operations:
- Make use of the INSERT command to contribute information to the database.
- Make use of the SELECT command to get data from the source database.
- Through the use of the UPDATE command, the data in the database may be updated.
- DELETE is the command that should be used to delete data from the database.
Example: Introduce them to the student values (111, ‘George’, ‘Computer Science’)
- Can you explain the function of the DCL language?
Users can regulate access to the database as well as permission management via the use of data control language.
It is the subset of a database that determines which portion of the database should be accessible by which user at what moment in time.
It is also known as information access control. GRANT and REVOKE are the two commands that are included in it.
GRANT: It allows system administrators to provide rights and responsibilities to certain user accounts so that those accounts may carry out particular activities and operations on the database.
System administrators can revoke privileges and roles from user accounts via the REVOKE command. This prevents users from being able to utilize the permissions that were previously allocated to them on the database.
Example: I want to grant javatpoint@localhsot a grant on mydb.student.
- Do you have any idea what the database’s tables and columns are?
A table is a collection of data that is structured in the form of rows and columns, respectively. It allows users to store records in structural format and display them respectively.
It is comparable to worksheets that are often seen in spreadsheet applications. Rows are the tuples representing the basic data item, and columns are the attributes of the data items present in a given row. In this context, rows refer to more than one data item.
Columns may be classified as vertical, while rows are considered horizontal.
The components that make up the table’s structure are called fields. The same data type is used to hold the same category of information all the time.
Although a table has a predetermined number of columns, it may have any number of rows referred to as records.
Another name for it is a column, and it is located in the table of the database. It is a representation of the character or qualities that are associated with the entity in the record.
Example: Student Table: Table
Stud_rollno, Stud_name, Date of Birth, Branch, and other information are included in this field.
- What exactly is a main key, then?
A field or the combination of fields used to identify each record in the table uniquely is referred to as a primary key. There is no other key just like it; it is one of a kind.
The column can’t be null or empty if it currently includes a primary key. While a table can include duplicate columns, having more than one primary key is not permitted.
Every time, it records values that are unique in a column. For instance, the ROLL number might be considered the main key for a student enrolled in a college or university.
Conclusion
Proficiency with SQL is a must for data analysts and data scientists and could significantly improve employment possibilities in data analysis.
Preparing for SQL interview questions is important to showcase your skills and problem-solving capabilities to prospective employers.
By studying and preparing the questions in this article, you may effectively handle SQL interviews and succeed in your data analyst or data scientist position.
At Interview Forge, we’re all about helping you ace your job interviews with confidence. Our blog offers practical tips, personalized interview questions, and real-world advice to get you ready for your next big opportunity. Whether you’re new to the job market or just looking to level up, we’ve got you covered!
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