You can instruct the container to connect to an existing SQL Server and database instead of using the SQL Server inside the container, which will also mean that the SQL Server inside the container will not be started. This is needed if you want to connect multiple instances to the same database, but also makes a lot of sense if you want to run a lot of containers on the same host. Otherwise, you will have one SQL Server running per container, which will need a lot of resources.
In this section, I am assuming there is a SQL Server (in a container or not) called sqlserver running in your local environment where the Business Central container can reach it. I have a SQL user called sqluserwith a password of 1SuperSecretPwd!, who has the necessary rights to access a Business Central database called FinancialsW1 on that server. For this scenario...