DECLARE @DB_NAME NVARCHAR(128) = N'Test_DB'
DECLARE @Sql NVARCHAR(MAX);
IF DB_ID(@DB_NAME) IS NULL
BEGIN
SET @Sql = N' CREATE DATABASE ' + QUOTENAME(@DB_NAME)
EXECUTE sp_executesql @Sql
END
Important Note
Make sure your database name is in accordance with the Rules for Regular Identifiers