How to Repair Corrupt SQL Database Files in Simple Steps

What Causes SQL Database Corruption?

Your SQL Database can be affected by several incidents that can cause damage and corruption. The possible factors for a corrupted SQL database and its symptoms are:

• Abrupt power cuts, sudden shutdowns, and bugs in the software can be the reasons.
• Often, viruses and threats corrupt the files located within the SQL database.
• Physical damage to the disk or bad sectors on the hard drive can cause hardware issues.
• Network failures during the running operations due to connection or login errors also cause damage.
• Sometimes, the inappropriate isolation level of the SQL Server also affects the database.

These issues affect the database, resulting in I/O subsystem failures, accidental data deletion, and SQL memory issues. Furthermore, the transaction log is impacted, and page-level corruption can occur, too. So, it is necessary to fix the corrupted SQL database to avoid severe losses.

How to Recover SQL Database from Corruption?

The main task for DB administrators is to keep the database in a healthy state. Yet, many scenarios lead to its corruption. Regardless, you wish to restore databases with minimal possible downtime and losses. Here, we’ve outlined two reliable ways to repair corrupt SQL files manually and professionally. We’ve also highlighted the common challenges encountered by the users during the SQL recovery.

Repair Database in SQL Server Manually

There are two major ways for you to restore databases from the SQL Server after it faces corruption. The first way is through a backup or SQL logs, and another one includes using the DBCC CHECKDB command. Both processes are discussed in detail as follows:

Method 1: Repair SQL Server Database from Backup Logs

1. Open SSMS and run the command EXEC sp_readerrorlog to check the errors.
2. If an issue or error is diagnosed, then restore it from the last backup by the command:
   RESTORE DATABASE TestDB_Name FROM DISK = ‘C:\Backup\Test_DB.bak’ WITH REPLACE

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If the error is resolved and the repair SQL file is successful, then no worries. Otherwise, go for the next solution.

Method 2: Using DBCC CHECKDB to Recover SQL Database

1. Run the SQL Server Management Studio (SSMS) from the Start menu.
2. Next, set the database to Emergency mode to provide read-only permissions by the command:
   ALTER DATABASE (DB NAME) SET EMERGENCY

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3. Further, run the DBCC CHECKDB (DB NAME) WITH NO_INFOMSGS, ALL_ERRORMSGS query to identify the inconsistencies and errors.

Note: It will also recommend a repair level. There are three different repair levels available with the DBCC CHECKDB command that help make the database functional.

4. But, to bring the data back, first, switch it to single-user mode from emergency mode. To do so, run the command given here:
   ALTER DATABASE (DB NAME) SET SINGLE_USER WITH [ROLLBACK IMMEDIATE]

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5. Afterward, run the given command to repair minor database corruption issues with no loss:
   DBCC CHECKDB (DB NAME, REPAIR_FAST) WITH ALL_ERRORMSGS, NO_INFOMSGS; GO

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6. If it doesn’t work, then run the command with less data loss risk:
   DBCC CHECKDB (DB NAME, REPAIR_REBUILD) WITH ALL_ERRORMSGS, NO_INFOMSGS;

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Note: The next command can be run even in the Emergency mode. It will recover the SQL database and resolve the corruption, but there may be some losses.

7. Furthermore, for deep corruption, you can run the following command:
   DBCC CHECKDB (DB NAME, REPAIR_ALLOW_DATA_LOSS) WITH ALL_ERRORMSGS, NO_INFOMSGS; GO

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8. In the end, set the SQL database back to multi-user mode with the command:
   ALTER DATABASE (DB NAME) SET MULTI_USER

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Following the above procedures, you can repair a corrupt SQL database, but there are some cons to it.

Shortcomings of the Manual Method

• Not suitable for severely corrupted SQL databases and cannot repair deleted objects.
• Users must have technical knowledge and proficiency to execute the commands.
• Sometimes, can result in the deallocation of rows and pages that are unrecoverable.
• No guarantee of accurate recovery. Also, leaves the database in an inconsistent state.

Thus, it is necessary to choose a good alternate, like a professional tool, in case the DBCC CHECKDB fails.

How to Recover SQL Database with a Repair Tool?

There are many situations when DBCC CHECKDB doesn’t prove to be a reliable solution. At such times, the SysInfo SQL Database Recovery Tool comes in handy. It is a quick, secure, and effective way to repair corrupted databases without losses. The utility ensures the maintenance of the file structure and integrity. Additionally, it supports both MDF and NDF database files and recovers all the tables, records, rows, columns, etc. Moreover, the tool enables several beneficial features to the users, such as:

• Restore deleted records from the SQL database files at once.
• Convert MDF to SQL Script or save in a previous or new Database.
• Supports all SQL Server versions: 2017, 2016, 2014, 2012, 2008, and others.

Steps to Repair Database in SQL Server

1. Run the MS SQL Database Repair Tool and click Open to add the MDF file.
2. Next, select a recovery option: Standard or Advanced to repair the file.
3. Further, choose other filters and click OK to proceed to recovery.
4. Expand the tree structure and preview records and other database items.
5. Afterward, click Save SQL Data and choose an option: Database or Scripts.
6. Specify other details and filter as per the need. At last, click OK.

Know more: Fix Microsoft SQL Error 3456

Conclusion

To sum up, it’s evident from the blog that various causes give rise to SQL database corruption. Due to this, users need to take appropriate measures to recover the SQL database. There is a chance that the manual method fails and does not provide the desired outcomes. In that case, use a professional tool and perform a risk-free and hassle-free SQL data recovery.

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About The Author:

Simran Bhatia

Simran Bhatia is a technical content writer engaged in writing clear, concise, and SEO-optimized content. With a background in computer science and a passion for writing, I thrive to deliver complex technical content in simple layman terms.