employee_id	name	age	department
1	John Doe	30	HR
2	Jane Smith	35	Finance
3	Michael Lee	40	IT

SELECT Statement

The SELECT statement is used to retrieve data from one or more tables in a database.

Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition;

Example

SELECT * FROM employees WHERE department = 'IT';

This query selects all columns from the “employees” table where the department is ‘IT’.

Output

3|Michael Lee|40|IT

INSERT Statement

The INSERT statement is used to add new records into a table.

Syntax

INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);

Example

INSERT INTO employees (name, age, department) 
VALUES ('Sarah Johnson', 28, 'Marketing');

This query inserts a new employee record into the “employees” table with specified values.

Output

To see, if the new data has been successfully inserted, you can execute the SELECT command, like this

SELECT * FROM employees;

Now, you’ll get the entire table and you can see that the new data has been added to the database

1|John Doe|30|HR
2|Jane Smith|35|Finance
3|Michael Lee|40|IT
4|Sarah Johnson|28|Marketing

UPDATE Statement

The UPDATE statement is used to modify existing records in a table.

Syntax

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

Example

UPDATE employees
SET department = 'Operations'
WHERE name = 'Michael Lee';

This query updates the department of the employee named ‘Michael Lee’ to ‘Operations’.

Output

Let’s run the SELECT command to see the updated database

SELECT * FROM employees;

You can see that, the database has been updated and now Michael’s department is set to Operations

1|John Doe|30|HR
2|Jane Smith|35|Finance
3|Michael Lee|40|Operations
4|Sarah Johnson|28|Marketing

DELETE Statement

The DELETE statement is used to remove existing records from a table.

Syntax

DELETE FROM table_name
WHERE condition;

Example

DELETE FROM employees
WHERE age > 35;

This query deletes records from the “employees” table where the age is greater than 35.

Output

Execute the SELECT command to check the updated database:

SELECT * FROM employees;

You can see that Michael has been removed from the database as he is the only one with an age over 35.

1|John Doe|30|HR
2|Jane Smith|35|Finance
4|Sarah Johnson|28|Marketing

Frequently Asked Questions on Query in DBMS – FAQs

What is a query in DBMS?

A query in a DBMS is a request made by a user or application to retrieve or manipulate data stored in a database. This request is typically formulated using a structured query language (SQL) or a query interface provided by the DBMS.

What is SQL?

SQL (Structured Query Language) is a standardized programming language used to interact with relational databases. SQL provides a set of commands for querying, updating, and managing databases.

What are the major SQL commands?

The major SQL commands include SELECT, INSERT, UPDATE, and DELETE. These commands are used for retrieving, adding, updating, and deleting data from a database, respectively.

How can I retrieve data from a table in SQL?

To retrieve data from a table in SQL, you can use the SELECT statement. For example, `SELECT * FROM table_name;` retrieves all columns from the specified table.

How do I view the entire data of a table in SQLite?

To view the entire data of a table in SQLite, you can use the SELECT statement without specifying any specific conditions. For example, `SELECT * FROM employees;` displays all rows and their corresponding data in the “employees” table.