SQL repair is a necessity that is demanded in a situation where access to MDF file is lost and no alternative is available to make it usable. Although as far as you have a recent and updated backup for your SQL Server database restoring database from a faulty state is absolutely possible. But rolling back any changes or incorrect processing carried out turns out next to impossible when backup isn’t available.
One Such Situation
Suppose, you have executed a DROP statement to either remove or deleted indexes, database and tables from your MDF file. But it was later discovered that objects of your database got modified in the process of carrying out DROP statement.
Unavailability of an updated backup file may prove to be a disastrous situation for you, but fortunately there is still a way to rollback the changes that have been made; even if you don’t have a backup.
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How Does It Work?
The transaction log of your SQL Server keeps a record logged about each DROP operation that has been carried out on the database objects. Basically this means that a transaction log has all the information that would be required for rolling back a change. And as it is in FULL recovery mode it also supports the point-in-time SQL repair from DROP operations too.
A DROP operation can be rolled backup only if its encapsulated entry has been logged in as an active transaction (that is still in process). However, using an SQL query will only result in showing an error message for the dropped table.
But if you use an SQL code it will return the rows of your table as soon as it rolls back your DROP operation on it.
Although, the procedure is executable but only if the DROP operation was uncommitted. You can rollback specific changes from an active uncommitted encapsulated DROP operation. But if it was committed all of the changes made will be rolled back and you will have to start from the beginning all over again.
Conclusion: Changes can be rolled back but if inaccessibility of your database is a result of damage caused in it or loss of data then it can only be reverted back via Repair SQL Database. And to do the same you will have to execute recovery of your database which is accurately doable only via using commercial solutions like SQL Recovery program.