Saving Changes is not permitted. The changes you have made require the following tables to be dropped and re-created.

In SQL Server if you attempt to modify a table structure through the Table Designer you would encounter this error.

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There is a simple fix for it.

 

Step 1 Go to Tools > Options

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Step 2

Go to Designer > Table and Database Designers

and Untick the option

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Step 3: Now you should be able to save the changes to your tables.