What is a query?

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Sep 15, 2025

Nabilla R. & Ariffud M.

4min Read

A query is a request for information or an action from a database or search engine. In plain English, a query is simply a question. In a technical context, it’s a specific command sent to a system to retrieve data or perform a task.

To communicate with a database, you must write these requests in a specific query language, such as Structured Query Language (SQL).

Understanding how queries function involves a few core concepts:

Mechanism. Queries operate on a simple request-process-output flow to retrieve information or perform actions. Main types. These include Select queries to fetch data and Action queries (INSERT, UPDATE, DELETE) to modify it. Query languages. The primary languages are SQL for relational databases and NoSQL for non-relational ones.

Though people also use query to mean a question entered into a search engine, the term most often refers to a request sent to a database.

For a visual explanation of what a query is, check out this video from Hostinger Academy.

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How does a query work?What are the different types of queries?Query languagesQuery examplesHow do queries work in databases?

How does a query work?

A query works by sending a structured request in a specific language. A system, such as a database, processes the request and returns the needed information or performs an action.

Think of it like ordering at a coffee shop. When you ask for an Americano, you are making a request (a query). The barista understands your language, makes the coffee (processes your request), and gives you your drink (the output).

A database query works the same way: As long as you and the database “speak” the same language, you can request information, and the system provides it.

This process follows a simple flow:

Request. You write a command in a query language to ask for specific data. Process. The database management system (DBMS) interprets your command. Output. The system retrieves the data or performs the action and returns a response.

What are the different types of queries?

The main types of database queries are Select queries, which retrieve data, and Action queries, which modify data. You can also combine these operations to perform more complex tasks.

Here are the most common types and the SQL commands that define them:

Select query. The most common type of query. It fetches data from one or more tables in a database without changing the data itself. Example: Use the SELECT command to get everyone’s names and occupations in a Participant table. Action queries. These queries manipulate data, such as creating, changing, or deleting records. Insert query. Adds new records or rows to a table using the INSERT INTO command. Update query. Modifies existing records in a table with the UPDATE command and specific criteria. Delete query. Removes one or more records from a table with the DELETE command, permanently erasing the data. Combined query. This query uses a SELECT statement inside an Action query to identify which records to modify. Developers often achieve this with a subquery in the WHERE clause. Example: Use UPDATE to change the status of all employees in a Sales department, where the department ID is first found using a SELECT subquery.

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UPDATE Employees

SET Status = 'Inactive'

WHERE DepartmentID IN (SELECT DepartmentID FROM Departments WHERE DepartmentName = 'Sales');

UPDATE Employees SET Status = 'Inactive' WHERE DepartmentID IN (SELECT DepartmentID FROM Departments WHERE DepartmentName = 'Sales');

UPDATE Employees SET Status = 'Inactive' WHERE DepartmentID IN (SELECT DepartmentID FROM Departments WHERE DepartmentName = 'Sales');

Query languages

To write a query, you need a query language. While several exist, the most common follow either SQL or NoSQL principles.

SQL is the standard language for relational databases. These databases store data in tables with rows and columns.

It’s important to note the difference between SQL and MySQL: SQL is the query language, while MySQL is a popular database management system that uses SQL.

NoSQL (Not Only SQL) refers to languages designed for non-relational databases. These databases handle data more flexibly and store unstructured formats, such as documents or key-value pairs.

A NoSQL database works well when your data doesn’t fit neatly into tables.

Other specialized query languages include ArangoDB Query Language (AQL), Datalog, and Data Mining Extensions (DMX).

Query examples

Let’s look at some practical SQL query examples. Suppose you have a database table named Participant with the following data:

IDNameSexAgeOccupation1JohnMale17Student2PeterMale26Unemployed3MargarethFemale34Teacher4LeaFemale34Unemployed

Selecting specific data

To retrieve only the Name and Occupation columns from the Participant table, you would use a SELECT query.

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SELECT Name, Occupation FROM Participant;

SELECT Name, Occupation FROM Participant;

SELECT Name, Occupation FROM Participant;

The result would be a new table with only the requested data:

NameOccupationJohnStudentPeterUnemployedMargarethTeacherLeaUnemployed

Deleting data

To remove all participants whose occupation is Unemployed, you would use a DELETE query with a WHERE clause to specify the condition.

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DELETE FROM Participant WHERE Occupation = 'Unemployed';

DELETE FROM Participant WHERE Occupation = 'Unemployed';

DELETE FROM Participant WHERE Occupation = 'Unemployed';

This command removes the matching rows, leaving this result:

IDNameSexAgeOccupation1JohnMale17Student3MargarethFemale34Teacher

Inserting new data

To add a new row to the table for a participant named Mario, you would use an INSERT INTO query.

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INSERT INTO Participant (ID, Name, Sex, Age, Occupation)

VALUES (5, 'Mario', 'Male', 29, 'Plumber');

INSERT INTO Participant (ID, Name, Sex, Age, Occupation) VALUES (5, 'Mario', 'Male', 29, 'Plumber');

INSERT INTO Participant (ID, Name, Sex, Age, Occupation) VALUES (5, 'Mario', 'Male', 29, 'Plumber');

The Participant table would then include the new record.

IDNameSexAgeOccupation5MarioMale29Plumber

Updating existing data

To change Margareth’s occupation to Headmaster, you can use an UPDATE query. The WHERE clause modifies only the correct record.

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UPDATE Participant SET Occupation = 'Headmaster' WHERE ID = 3;

UPDATE Participant SET Occupation = 'Headmaster' WHERE ID = 3;

UPDATE Participant SET Occupation = 'Headmaster' WHERE ID = 3;

The query finds the row with ID = 3 and updates the Occupation field.

IDNameSexAgeOccupation3MargarethFemale34Headmaster

A note on search engine queries

It’s also worth noting that the term “query” is used differently for search engines. A search engine query is simply the word or phrase you type into the search bar.

Unlike database queries, these don’t require a special language – the search engine’s algorithm processes your natural language to find relevant results.

How do queries work in databases?

In a database, a query works when a DBMS interprets your command, scans the relevant tables for matching data, and returns the results. The DBMS acts as the software interface between the user and the database, handling all of these requests.

MySQL is one of the world’s most popular open-source relational DBMS. To get a complete picture of the platform where these commands operate, we recommend you to learn what MySQL is.

All of the tutorial content on this website is subject to Hostinger's rigorous editorial standards and values.

The author

Nabilla R.

Nabilla is a website hosting and development enthusiast. She loves to share her knowledge with others in order to help them grow their online presence. When she's not busy writing, Nabilla enjoys exploring nature and going on adventures. She is passionate about helping people achieve their online goals.

The Co-author

Ariffud Muhammad

Ariffud is a Technical Content Writer with an educational background in Informatics. He has extensive expertise in Linux and VPS, authoring over 200 articles on server management and web development. Follow him on LinkedIn.

网址：What is a query? https://c.klqsh.com/news/view/285607

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