content database in sharepoint
A content database in sharepoint is not the database server itself but container for all the content for a single web application.
You can have only one content database for one web application however, you can separate content for multiple websites into multiple content databases for a site collection. You can also use a single content database for multiple site collections, keeping in mind that the site collection or collections represent a single web app.
we can run the powershell command as below to get quick details however can get from “Central Admin -> Application Management” under “View all Site Collections”.
Isolation and sharing are expressed as the difference between one site collection using one database and numerous site collections sharing a database. The number of site collections using a database is also a scaling and performance issue. If you are deploying site collections with a high workload attached and greater expectancy for growth, make sure to use fewer site collections per database. You can also plan your content database strategy by adding databases to site collections as they grow or associate specific site collections only with specific content databases. The latter approach lets you isolate a database serving particular site collections from all the other databases and thus isolate the content it contains.
boundaries and limits content databases
There can be 500 content databases per farm at max. With 200GB data per content database and 100TB of data per farm. 60 million items including documents and list items. Number of site collections per content database recommended to 5,000. However, up to 10,000 site collections are supported.2500 non-Personal site collections and 7500 Personal Sites or 10000 Personal Sites alone. find in details from Microsoft Doc Link.
content database for each site collection powershell
We can run below powershell command to know which content database your site collection attached to.
$site = Get-SPSite "http://win2016:37344/sites/SPmcse" write-host $site.WebApplication.ContentDatabases or $url="http://win2016:37344/sites/SPmcse" (Get-SPSite $url).ContentDatabase.name