the row values updated or deleted either do not make the row unique or they alter multiple rows

I want to delete row and I get this error:

the row values updated or deleted either do not make the row unique or they alter multiple rows

Answer

There are duplicate rows in your table. When this is the case you cannot edit table using UI. first delete rows with matching data using SQL then try and edit. Delete rows with matching data one by one until you are left with one row. Use the following query for deleting matching rows where column IdSeminar has value 1 :

Delete top(1) from tab where IdSeminar=1

do the same with other matching rows.