-1st Normal Form: The database contains at least one table that is an exact copy of another table, except with additional columns.

-2nd Normal Form: The database contains at least one table that is a corrupt, out-of-date copy of another table, except with additional columns. It is impossible to determine if these additional columns can be trusted.

-3rd Normal Form: The database contains at least one table whose name contains the string _v1 and another table whose name contains the string _v2 . At least one column in the _v1 table must be an undeclared foreign key that refers to rows that no longer exist in any other table.

-4th Normal Form: The database contains at least one table that has two or more columns whose contents are exactly the same, except that one of the columns has a name that is a misspelling of the other column’s name.