What Is the Definition of a Database Query?

Use an SQL SELECT statement to find the information you're looking for

Database Planning
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A database query extracts data from a database and formats it in a readable form. A query must be written in the language the database requires; usually, that language is Structured Query Language (SQL).

For example, when you want data from a database, you use a query to request that specific information. Perhaps you have an employee table, and you want to track sales performance numbers. You might query your database for the employee who recorded the highest sales in a given period.

The SQL SELECT statement

A database query must follow the query format that the database requires. The most common format is the Structured Query Language (SQL) standard query format that many database management systems use. SQL is a powerful language capable of advanced queries. 

SQL uses a SELECT statement to select specific data.

Consider an example based on the Northwind database that frequently ships with database products as a tutorial. Here's an excerpt from the database's employees table: 

 
EmployeeIDLastNameFirstNameTitleAddressCityRegion
1DavolioNancySales Representative507 20th Ave. E.SeattleWA
2FullerAndrew

 

Vice President, Sales
908 W. Capital WayTacomaWA
3LeverlingJanetSales Representative722 Moss Bay Blvd.KirklandWA

To return an employee's name and title from the database, the SELECT statement would look something like this:

SELECT FirstName,LastName,Title FROM Employees;

It would return:

FirstNameLastNameTitle
NancyDavolioSales Representative
AndrewFullerVice President, Sales
JanetLeverlingSales Representative

To refine the results further, you might add a WHERE clause:

SELECT FirstName,LastName FROM Employees
WHERE City='Tacoma';

It returns the FirstName and LastName of any employee who is from Tacoma:

FirstNameLastName
AndrewFuller

Note that SQL returns data in a row/column form that is similar to Microsoft Excel, making it easy to view and work with. Other query languages might return data as a graph or chart.

The Power of Queries

A database has the potential to reveal complex trends and activities, but this power is only harnessed through the use of the query. A complex database consists of multiple tables storing a myriad of data. A query allows you to filter the data into a single table so that you can analyze it more easily.

Queries also can perform calculations on your data or automate data management tasks. You can also review updates to your data before committing them to the database.