With VerifyOnly Data Validation Prior to Taking Backups More Details on CHECKSUM and BACKUP CHECKSUMįrom Disk='G:DBABackupsTestDBFull_MMDDYYYY.bak' Additionally, if available, the page checksum can be verified as well. This will check data pages contained in the backup file and compare it against the CHECKSUM used during the backup. CHECKSUM on Restore – Databases where BACKUP WITH CHECKSUM have been performed can then be additionally verified as part of the restore process.VERIFY too can be automated to perform each time your backups utilizing CHECKSUM run. Despite the name “RESTORE VERIFONLY”, it does not actually restore the data. Note that much like CHECKSUM, this will check to see if there are errors during the read/write process of the backup however, it will not verify that the data itself is valid or not corrupt.

This will verify the backup header, and also that the backup file is readable. VERIFY – It is not wise to rely solely on CHECKSUM, a good addition is to use RESTORE VERIFYONLY.To Disk='G:DBABackupsTestDBFull_MMDDYYYY.bak' BEWARE though, this does not ensure that the database is corruption free, CHECKSUM only verifies that we are not backing up an already-corrupt database. ( Later in this post we discuss checking data for corruption.) If it seems like too much trouble to write a CHECKSUM script every time you want to perform a backup, keep in mind that these can be automated as SQL Agent Jobs! A sample T-SQL script for using CHECKSUM is as follows:.If the backup completes successfully, there are no broken page checksums. If a bad checksum is found, the backup will fail. CHECKSUM is part of a backup operation which will instruct SQL Server to test each page being backed up with its corresponding checksum, making sure that no corruption has occurred during the read/write process. Backup with CHECKSUM – It may not be realistic to run regular test restores on every single database, this is where CHECKSUM is your friend.Make sure to run a test restore on your Full, Differential, Point in Time, and Transaction Logs! “Bonus points” if you automate refreshing non-production. If your Restore is successful, you have a solid backup. RESTORE – The most effective way to validate that your backups are good is to run a test Restore.There are several methods for validating your Backups. Corrupt backups are recoverable, but worthless. How do you know if your Backups are good? TEST! Validating SQL Server Backups will ensure that you are in a good place when it is time to bring your database back from the dead!ĭon’t assume that your Backups are solid and let them sit on a shelf. Here is the result set.You have your SQL Server Backup Plan and your Database Recovery Model set. Get the checksum of the modified column. SELECT CHECKSUM_AGG(CAST(Quantity AS INT)) Get the checksum value before the column value is changed. These examples use CHECKSUM_AGG to detect changes in the Quantity column of the ProductInventory table in the AdventureWorks2019 database. For more information, see Aggregate Functions (Transact-SQL). However, a small possibility exists that the calculated checksum will not change.ĬHECKSUM_AGG has functionality similar to that of other aggregate functions. If an expression list value changes, the list checksum value list will also probably change. Also, CHECKSUM_AGG functions allow the use of the DISTINCT keyword and the GROUP BY clause. The CHECKSUM_AGG result does not depend on the order of the rows in the table. RemarksĬHECKSUM_AGG can detect changes in a table. Returns the checksum of all expression values as int. CHECKSUM_AGG does not allow use of aggregate functions or subqueries. Specifies that CHECKSUM_AGG returns the checksum of unique values.Īn integer expression. ArgumentsĪpplies the aggregate function to all values.

To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation.

Sql checksum