DBCC CHECKDB checks the logical and physical integrity of all the objects in the specified database. If DBCC CHECKDB ran on database user should not run DBCC CHECKALLOC, DBCC CHECKTABLE, and DBCC CHECKCATALOG on the database as DBCC CHECKDB includes all the three commands. Usage of these included DBCC commands is listed below.
DBCC CHECKALLOC – Checks the consistency of disk space allocation structures for a specified database.
DBCC CHECKTABLE – Checks the integrity of all the pages and structures that make up the table or indexed view.
DBCC CHECKCATALOG – Checks for catalog consistency within the specified database. The database must be online.
Along with above three DBCC commands it also runs following two tasks to check the validity database (physical as well logical) i.e. validates the contents of every indexed view in the database and Validates the Service Broker data in the database.
If the database DBCC check has returned any errors, the best solution is to RESTORE DATABASE from BACKUP. (Additional reading: SQL Backup and Restore). There is additional keyword REPAIR with DBCC CHECKDB which can be used to repair database but it is not recommended. I will write additional articles on this subject.
Reference : Pinal Dave (http://blog.SQLAuthority.com)