SQL Server does not allow you to save changes. You must delete the changes and recreate the following tables.

After creating a table on SQL Server, you often need to change the design of the table. If you have any questions, the system will prompt "you are not allowed to save the changes. You must delete the changes and recreate the following tables. The reason is that, to prevent data tables from being changed at will, the structure of the table cannot be changed after creation by default. Therefore, you only need to cancel the operation to solve this problem. Details:
Tool menu -- option -- designers (designer) -- to prevent changes to the Save requirement for recreating the table, uncheck this option.