-- Set to single-user mode
ALTER DATABASE yourdatabasename
SET SINGLE_USER WITH ROLLBACK IMMEDIATE
GO
-- change collation
ALTER DATABASE yourdatabasename
COLLATE Turkish_CI_AS;
GO
-- Set to multi-user mode
ALTER DATABASE yourdatabasename
SET MULTI_USER WITH ROLLBACK IMMEDIATE;
GO
--Verify the collation setting.
SELECT name, collation_name
FROM sys.databases
WHERE name = yourdatabasename';