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Database Files-Heart of SQL Server Database


A database file is one of the many variants of the system object type *FILE. Descriptions of how a program's input data and output data are to be transferred to internal storage from a program are contained in a database file.

The primary data file and any secondary files not placed in other filegroups are part of the same filegroup. Data files can be grouped using user-defined filegroups for administrative, data allocation, and placement purposes.

The various types of database files and file groups will be discussed in detail in the following paragraphs. For additional research, about career in Microsoft SQL Server Database domain, a comprehensive SQL career path will help you explore all the career options.

What are Database Files?

The content of a database is structured in separate tables and fields using data files called database files. Dynamic websites like Facebook, Twitter, and others frequently use database files. to keep records.

The file extensions ".DB," "NSF," and others are among the most widely used for database files.

How are Database Files Used?

Data files contain data and objects such as tables, indexes, stored procedures, and views. Log files contain the information required to recover all transactions in the database.

How to Open a Database File

To quickly view or edit SQL files, you can open them in a text editor like Notepad or TextEdit. You can also open SQL files in MySQL Workbench to use MySQL's database editing tools or import an Azure SQL database into an Excel workbook.

Some Common Database Files


File Types


MySQL InnoDB Table


Microsoft Access Report


Data Definition language file


SQL Server database file


Database file


Structured query language data file

We will start our discussion with MySQL database files.

MySQL Database files

The entire database-related data and metadata are stored in a single folder whenever the MySQL database is installed. The actual database schema with a few values is shown here. Let's investigate it further.

The file extensions are as follows: 

.frm – The file extension that contains the table's schema or definition.

.myd – This is the file extension containing MyISAM table data.

.myi – This is the file extension containing MyISAM table indices.

Some MySQL Server 5.5/data/mysql folder files are *.frm, *.MYD, and *.MYI, with the asterisks representing actual table names. All of the above files will be in the data folder if the MyISAM engine is used, but files will be in the folder if InnoDB is used.

When a database is upgraded or moved, these files are used as backups to safeguard the schema, data, and indexes. The MySQL configuration files for Windows and Linux are named my. conf and my.ini, respectively.

SQL Server Database Files

At least two operating system files are in every SQL Server database: a log file and a data file. Log files contain the information required to recover all database transactions. Data and objects like stored procedures, views, tables, and indexes are contained in data files. Data files can be organized using filegroups for administration and allocation.

SQL Server databases have three types of files, as shown in the following table.




It contains startup information for the database and points to the other files. Every database has one primary data file. The recommended file name extension for direct data files is .mdf.


Optional user-defined data files. Data can be spread across multiple disks by putting each file on a different disk drive. The recommended file name extension for secondary data files is .ndf.

Transaction Log

The log holds information used to recover the database. There must be at least one log file for each database. The recommended file name extension for transaction logs is .ldf.

A straightforward database by the name of Sales, for instance, has a primary file that contains all data and objects and a log file that contains information from the transaction log. One primary and five secondary files comprise the more complex database known as Orders. The data and objects of the database can be found in all six files, and the transaction log data can be found in the four log files. Still have doubts regarding career benefits, average SQL developer salary, and the top companies hiring SQL developers around the world? Get in touch with our consultant today!

When handling single-disk systems, data, and transaction logs are typically stored on the same drive and path. There might not be better options for environments used in production. We suggest that you put information and log records on discrete circles.

  • The filegroup contains the primary data file and any secondary files that aren't put into other filegroups.
  • User-defined filegroups can be created to group data files together for administrative, data allocation, and placement purposes.

For instance: It is possible to create Data1.ndf, Data2.ndf, and Data3.ndf on three distinct disk drives and assign them to the filegroup fgroup1. After that, a table tailored to the filegroup fgroup1 can be created. Inquiries for information from the table will be spread across the three circles, making things run better. Using a single file created on a RAID (redundant array of independent disks) stripe set yields the same performance boost. However, you can easily add new files to new disks using files and filegroups.

How to Check The Location of SQL Server Database Files

Next, we'll learn how to find the actual place of database log files. For this, we'll take into account the AdventureWorks database. The steps are listed below.

Step 1

Log in to SQL Server Management Studio

Step 2

Select the database whose data files you want to examine in the object explorer. Right endlessly click on properties.

Step 3

The screen for database properties appears. To view the actual locations of the ldf and mdf files, select file.

Data File Pages

The allocated disk space for the data file in SQL Server is logically divided into pages. The pages are numbered in a logical order, starting with zero. Because each file has its specific ID number, page identification requires both the page number and the file ID. A record header is on the primary page of each document, and framework data is on the accompanying not many pages. The database boot page, which contains attributes, is stored in the primary data file and the first log file.


Database File Size

Each document extends in client-characterized development increases. The size of a file increases when it contains more data. You must also specify the maximum file size; if not, the record will continue developing until it consumes all suitable plate space.

Rules for designing files and file groups

The following rules pertain to files and filegroups:

  • Multiple databases cannot make use of the same file or filegroup. For instance, no other database can use the file sales.mdf and sales.ndf, which contains objects and data from the sales database.
  • A file can only belong to one file group at a time.
  • Files containing transaction logs are never included in any filegroups.

How to Backup a Database File

You can backup a single database file named ‘DataFile’ using the following Transact-SQL command:


FILE = 'DataFile' TO DISK = 'D:\DataFile.bak';

The other way to backup a database file is to use SQL Server Management Studio (SSMS): 

  • Right-click the database where you want to backup the filegroup.
  • Select “Tasks,” then “Back up….”
  • Select the backup type (“Full” or “Differential”)
  • Select “Files and filegroups.”
  • Choose a file and click “OK” (It is possible to select one or more individual files or select a filegroup to choose all the files in that filegroup automatically)


The preceding paragraphs taught us various aspects of database files and file groups. This will educate readers on the aforementioned subjects and inspire them to study more. We focused primarily on what is SQL Server data files, file groups, and MYSQL data files. 

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