SQL is relational database management system which store entire informations in the form of relations i.e. tables. You can store and manage huge amount of database in a simple way in SQL. All operation in this DBMS are performed with the help of query languages and SQL commands like Alter table, Drop table, Rename table etc. with the help of these commands you can easily communicate with the database and can perform specific task. With the help of Alter table command in SQL you can rename an existing table or you can also use this statement to modify or drop any column from existing table. This command is also used to change the one table property without affecting the other but sometimes it leads to SQL table corruption.

To understand the problem in detail consider a situation when you run Alter table command to change the value of column from Not NULL to NULL value but you didn’t get the required result. It might be possible that you receive records having null columns which you actually don’t want to extract. Execution of Alter table command in Sql sometimes also generates runtime errors like as follows:

• Error: 644, Severity: 21, State: 1 Could not find the index entry for RID…
• Error: 3314, Severity: 21, State: 4 Error while undoing logged operation in database ‘testdb’.
• Error: 9001, Severity: 21, State: 1 The log for database ‘testdb’ is not available.
• Error: 3314, Severity: 21, State: 5 Error while undoing logged operation in database ‘testdb’.

Usually such kinds of error messages appears when SQL server unable to synchronize column status between syscolumns and sysindex system table. Entire problems arises due to SQL table corruption which in turns corrupted the database and give rise to errors.

In order to resolve the errors and repair damaged table you can run DBCC DBREINDEX command along with repair clause. You can also run ALTER table Transact SQL command to change the column which is key of clustered index. If you still experience the similar error message after running Alter table command in SQL then it is clear that SQL table corruption is increased too much extent and you have to repair it using effective third party software. You can use MS SQL Database Repair Software to repair your damaged SQL table and can easily resolve the problem.