... constraint ensures that anything not aimed at a known person is classified as an individual subscription. Attribute Split RowsConsider this table, which directly models a sign-in/sign-out sheet. ... Use a few statements such as:INSERT INTO Foobar (a, b, c) VALUES ('a1', 'b1', 'c1');INSERT INTO Foobar (a, b, c) VALUES ('a2', 'b2', 'c2');INSERT ... 8, physical data independence). Dr. Codd s rules are discussed in Chapter 2. Early SQL products were built on existing file systems. The data was kept in physically contiguous disk pages, in...