Database management systems are essential for accessing and analyzing data. Relational databases continue to be among the extensively used systems in today’s world. Individuals who possess SQL skills are in high demand. So if you’re someone who has an upcoming interview, this blog covers the top SQL interview questions for beginners. These questions will help you revise your knowledge and ensure that you have strong foundational knowledge. Let us now look at the top SQL interview questions that will help you ace that interview.
SQL Interview Questions for Beginners
- How do you create a table in SQL?
If you wish to create a table in SQL, you must use the following command.
CREATE TABLE table_name (
column1 datatype,
column2 datatype,
….
);
First, you will use the keyword CREATE TABLE followed by the name of the table. Within brackets you can mention the name of the columns that you wish to have in the table followed by the data type. Let us understand this with the help of an example.
CREATE TABLE student (
name varchar(30),
age int,
gender varchar(25),
);
- How do you delete a row in SQL?
To delete a row in SQL, you will use a simple command known as the DELETE query. This will help you delete the existing rows in a table. Here is the format to be followed.
DELETE FROM table_name
WHERE [condition];
Here, we are using the delete query followed by the table name. We will then use the WHERE query to provide the condition to be followed while deleting the row. Let us look at an example for the same. If we wish to delete all the rows from the student table where the students’ age is equal to 25, we will use this command.
DELETE FROM student
WHERE [age=25];
- How do you insert the date in SQL?
INSERT INTO tablename (col_name, col_date) VALUES (‘DATE: Manual Date’, ‘2020-8-17’)”;
- What is the command used to view tables in SQL?
To view a table in SQL, you can use the following syntax.
Show tables;
- How can we delete tables in SQL?
To delete a table in SQL, we can use two methods. They are: DROP and TRUNCATE. Both of these commands are used for different purposes within SQL. If you wish to completely delete the table from the database, you can use the DROP TABLE table_name; command. This will delete all the data along with the table itself. If you want to delete the data which is within a table but not the entire table, you should use the TRUNCATE TABLE command.
- What do you mean by Normalization in SQL?
When you want to decompose a larger table that is complex, into a simple or smaller table, you can use normalization. It helps in removing the redundant data in a table. These smaller tables do not have any redundant information and contain only the unique information.
- How do I install SQL?
SQL is a structured query language and cannot be installed. To implement any SQL Query, your requirement is to have a relational database management system. Multiple relational database management systems are available to us today, such as:
- ORACLE
- MySQL
- SQL Server
Thus, if you want to implement an SQL query, you must install any of the above mentioned relational database management systems.
- How do you update data in SQL?
To update data, you must use the UPDATE command. This command comes under data manipulation language or DML and is part of SQL. The key purpose of the command is to allow us to update any existing data in a table.
UPDATE student
SET last_name=‘Sharma’
WHERE employee_id=202;
Thus, with the help of this command, we can change the last name of the student to sharma.
- How many types of SQL Queries are there?
There are four types of SQL Queries available. They are as follows:
- DDL or Data Definition Language
- DML or Data Manipulation Language
- DCL or Data Control Language
- TCL or Transaction Control Language
DDL helps us in the creation of objects, DML helps us manipulate or update data, DCL lets us assign and remove data, and lastly, TCL helps us in saving changes to a database. It also helps in restoring changes to a database.
- How do you create a Database in SQL?
A repository that contains multiple tables is known as a database in SQL. To create a database, you can use the following command:
CREATE DATABASE database_name;
Conclusion
This brings us to the end of the blog about SQL Interview Questions for Beginners. I hope you found this helpful and are now better equipped with the foundational knowledge about SQL. Happy Learning!
