Attach an existing content database to the farm using PowerShell script

The Mount-SPContentDatabase cmdlet attaches an existing content database to the farm. If the database being mounted requires an upgrade, this cmdlet will cause the database to be upgraded.

The default behavior of this cmdlet causes an upgrade of the schema of the database and initiates upgraded builds for all site collections within the specified content database if required. To prevent initiation of upgraded builds of site collections, use the NoB2BSiteUpgrade parameter. This cmdlet does not trigger version-to-version upgrade of any site collections.

Syntax:

Mount-SPContentDatabase [-Name] <String> [-WebApplication] <SPWebApplicationPipeBind> [-AssignmentCollection <SPAssignmentCollection>] [-AssignNewDatabaseId <SwitchParameter>] [-ChangeSyncKnowledge <SwitchParameter>] [-ClearChangeLog <SwitchParameter>] [-Confirm [<SwitchParameter>]] [-DatabaseCredentials <PSCredential>] [-DatabaseServer <String>] [-MaxSiteCount <Int32>] [-NoB2BSiteUpgrade <SwitchParameter>] [-SkipIntegrityChecks <SwitchParameter>] [-WarningSiteCount <Int32>] [-WhatIf [<SwitchParameter>]]

Example:

Mount-SPContentDatabase "MyDatabase" -DatabaseServer "MyServer" -WebApplication http://sitename

This example mounts an existing database to the sitename web application. If upgrades are required, it triggers database schema upgrade and then performs only build-to-build upgrade actions on existing site collections if required. This operation does not changed the CompatibilityLevel for existing site collections in this database.

Mount-SPContentDatabase "MyDatabase" -DatabaseServer "MyServer" -WebApplication http://sitename -NoB2BSiteUpgrade

This example mounts an existing database to the sitename web application but it prevents any site upgrades from occurring. If upgrades are required, it triggers database schema upgrades only and no build-to-build upgrade actions are performed on any site collections. This operation does not change the CompatibilityLevel for existing site collections in this database.

For More Info:

http://technet.microsoft.com/en-us/library/ff607581(v=office.15).aspx