How to check if a database exists in SQL Server?

Question

What is the ideal way to check if a database exists on a SQL Server using TSQL? It seems multiple approaches to implement this.

Answer 1

From a Microsoft's script:

DECLARE @dbname nvarchar(128)
SET @dbname = N'Senna'

IF (EXISTS (SELECT name 
FROM master.dbo.sysdatabases 
WHERE ('[' + name + ']' = @dbname 
OR name = @dbname)))

-- code mine :)
PRINT 'db exists'