A change log for every database records what changed, when, why, and by whom, with a simple table and a habit of updating it.
Designing a Database for Multiple Customers
A database for multiple customers can share tables, split schemas, or split databases; the choice balances isolation and operating cost.
Using Synonyms to Simplify Cross-Database Queries
Using synonyms can hide a cross-database object name from callers, but permissions, dependency checks, and deployment still need care.
Documenting a Database With Extended Properties
Keep extended properties beside your SQL Server schema, maintain table and column descriptions, and query a useful data dictionary.
Why You Should Name Default Constraints
Name default constraints so deployments can find them reliably, and replace system-generated names through a reviewed migration.