I have created a new site collection within a SharePoint 2013 web application and want it to use a new content database. After creating the new content database using the New-SPContentDatabase cmdlet I used the Move-SPSite cmdlet:
Move-SPSite –DestinationDatabase “”
Once complete I ran IISRESET in a command prompt, and verified the operation by using the Get-SPWebApplication cmdlet to list all site collections and their content databases:
Get-SPWebApplication | Get-SPSite | Format-Table -Property URL,ContentDatabase
Albandrod's Memory 