If you want to create a new site collection in the specific database, there are several different options available in the SharePoint 2010.
Option 1 => Central Administration (Good Approach)
From the central administration site, you can create the site collection in the specific database with the following workaround. The downside of this approach is you have to temporarily take down the all the content databases in the given web application except the database where you want to create the new site collection.
- Create a new content database for the given web application (Central Administration -> Manage Content Databases)
- Detach/remove the content databases except the new one (Central Administration -> Manage Content Databases)
- Create the new site collection from the central admin (Central Administration -> Create Site Collection)
- Attach/Add the offline content databases (Central Administration -> Manage Content Databases)
Option 2 => PowerShell (Better Approach)
Better way to approach creating the new site collection in the specific content database is to use New-SPContentDatabase and New-SPSite PowerShell commands.
- Step 1- Add New Content DB to the Web Application
New-SPContentDatabase -Name WSS_Content_Accounts -WebApplication http://sp2010vmStep
- Step 2- Create New Site Collection with Top Level Site Based on Team Site Template in the New Content DB
New-SPSite http://sp2010vm/sites/accounts -OwnerAlias “Niks\Administrator” -ContentDatabase WSS_Content_Accounts -Name “Account Sites” -Description “Account Sites Container” -Template “STS#0”
Hope this will be helpful.