How to repair a corrupt SQL Database?

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Repairing a corrupt SQL Server Database can be a tedious task if you don’t know the proper technique. There is a manual technique available to repair corrupt SQL databases but professional and authentic third-party software is always the best approach to do it. There are plenty of software available online for this purpose, but finding the best one is, again, a big task. Before knowing about SQL recovery solutions, you should know about SQL Server and reasons for its corruption.

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What is SQL Server?

SQL Server is a database management system primarily used for storing and retrieving data by other applications. Developed by Microsoft, SQL Server uses three types of files to store and manage data – Primary Files (MDF), Secondary Files (NDF) and Log Files (LDF).

• Primary SQL Server database files have MDF extension. Each database has one primary file, and it stores user data and objects, including Indexes, Columns, Views, Functions, Values, Tables, Keys, Stored Procedures, Triggers, Default Values, etc. MDF files also store the startup information for the database.
• Secondary files are optional and have .NDF extension. You can create an unlimited number of NDF files as per your requirement. Commonly used to spread data across multiple disks, NDF files can be used to store user data as well.
• Log files are basically the backup files of SQL Server database. They are used to restore the database in case of corruption. Log files have .LDF extension and store log information. Every database has at least one log file.

SQL Server databases can be corrupted due to various reasons. MDF files are the primary database files holding the user data, and their corruption can corrupt the entire database. Multiple reasons can cause MDF corruption, such as:

• Storage media corruption where MDF files are stored
• Storing SQL database in compressed folders
• Changes in SQL Server account
• Accidental data deletion
• File header corruption
• Bugs in disk drivers
• Network failure when database is in working condition
• Hard disk failure, sudden power failure, unexpected system shutdown, and virus attacks are some of the reasons that can cause MDF corruption.

In case of MDF corruption, SQL database becomes inaccessible. If you try to access the corrupt database, you might get different error messages. Some most common error messages are:

• Corruption on data pages
• Msg 823 error in SQL Server / Msg 824 in SQL Server / Msg 825 (read retry) in SQL Server
• Error 9004 in SQL Server
• SQL Server Table Corruption Error
• Metadata Corruption Error
• SQL Server Page Level Corruption

There are several other error messages you might get while trying to open a corrupt SQL database. If you’re a database administrator, you need to act immediately to prevent any data loss. Read on to know the solutions to restore a corrupt SQL database.

• Do not detach the database: Some users detach their SQL server from a database; it will corrupt and damage their database, and for that reason, they face corruption in the SQL Server.
• Never Restart SQL Server: When you are working on your SQL Server, you suddenly face some interruptions, and then you restart SQL Server without saving your data. It will damage and corrupt your SQL database, and after that, you can face many errors in your SQL database.
• Do not Shut down the SQL Server: Occasionally, users are working on their SQL Server, and suddenly, their system gets shut down; this will cause many significant problems in their SQL Server.

The main job of the Database Administrator is to keep the database highly secure and available. When there is corruption in database files, then sometimes it may not show any symptoms of error, but the data remains unavailable. That’s why the administrator should employ some methods that check the health of the database to find any errors or corruption.

1. Run the database backup along with CHECKSUM
   When the Administrator is running the database backup process, then the CHECKSUM command should also be included with the backup command. The CHECKSUM command will check the database for any corruption and stop the backup process if it finds any.
   BACKUP DATABASE XYZ
   TO DISK = ‘E:\Database Backup\XYZ.bak’
   WITH CHECKSUM;

   Run the command and see the results.

2. Run the DBDC CHECKDB command
   DBDC is the command to run the routine checkup of the database, and it detects several issues affecting the database.
   DBCC CHECKDB ;

   The command will check the physical and logical integrity of all the database objects like tables, triggers, relationships, and dependencies. Find any problem, then it will be shown in the result with the error message. The error message will clearly show the details, like why it showed the error and stopped the process from finishing.

There are few manual solutions to repair corrupt SQL databases, but they do not guarantee database recovery.

You can use the log files (NDF) of SQL Server to restore the database. However, log files are not sufficient enough to recover the database in many corruption cases. Sometimes, backup files also get corrupted if the corruption is severe.

Another way to repair the corrupt SQL database is using the database console commands i.e. DBCC CHECKDB and DBCC DEBREPAIR. They can be helpful for fixing minor SQL database corruption issues, but they aren’t very efficient though for all corruption cases. Performing database console commands requires specific technical knowledge which might be confusing for non-technical users.

Thus, using authentic third-party software is the best way to repair and recover corrupt or damaged SQL databases. It is the best software available to fix database corruption errors.

Kernel for SQL server recovery is probably the best software to deal with all kinds of SQL database corruption issues effectively. The software is extraordinarily programmed to fix all minor and major MDF (primary database files of SQL Server) file corruption issues with accuracy. Ensuring effortless database recovery in almost no time without causing any data loss, the software offers some really high-end features. In fact, the best and most remarkable aspect of the tool is its ability to restore all SQL database objects, including Tables, Columns, Indexes, Functions, Values, Keys, Views, Rules, Triggers, Stored Procedures, Checks, Default Values, User data types etc. Adding to that, it even provides complete support to restore multiple MDF files at the same time. No matter whether the size of databases is big or too big, the tool quickly repair MDF file of any size.

Conclusion:

In this blog, we have discussed SQL databases and their corruption. In the first part, we discussed what SQL server is and how an SQL database may become corrupt. We also tried to mention all the error notifications that a user may face while facing corruption. This may help the user identify corruption the next time. We have also mentioned the ways within which you can easily detect the database corruption. Lastly, we discussed the solutions with which you can fix the SQL database corruption. We mentioned the best, the quickest, and the safest way to deal with SQL database corruption. The tool has a user-friendly interface and comes with a trial version. Hope this blog was helpful. Let us know in comments about your queries and concerns.