1.The database principal owns a schema in the database, and cannot be dropped
2.User:sa trying to delete a user 'test' which exists in the db 'TestDB'
3.Run the below query to check the result:
USE [test]
GO
SELECT s . name
FROM sys . schemas s
WHERE s . principal_id = USER_ID ( 'ediuser' );
3.Run the following query to change the schema to dbo:
ALTER AUTHORIZATION ON SCHEMA :: db_owner TO dbo ;
ALTER AUTHORIZATION ON SCHEMA :: db_datareader TO dbo ;
4.after completed.it will allow to drop the user