Web site traffic - Figure 4-1: Insert anomaly occurs when detail record
Figure 4-1: Insert anomaly occurs when detail record added with no master record. . Delete anomaly Caused when a record is deleted from a master table, without first deleting all sibling records, in a detail table. The exception is a cascade deletion, occurring when deletion of a master record automatically deletes all child records in all related detail tables, before deleting the parent record in the master table. For example, referring to Figure 4-2, deleting an author requires initial deletion of any books that an author might already have published. If an author was deleted and books were left in the database without corresponding parent authors, the BOOK table records would become known as orphaned records. The books become logically inaccessible within the bounds of the AUTHOR and BOOK table relationship. Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov Isaac Azimov James Blish James Blish Larry Niven Larry Niven Larry Niven J.K. Rowling J.K. Rowling Harry Potter INSERT Book Add the book once the author added Add new author first Foundation Foundation Foundation Foundation Foundation Foundation Foundation Foundation and Empire Foundation s Edge Prelude to Foundation Second Foundation A Case of Conscience Cities in Flight Footfall Lucifer s Hammer Ringworld 893402095 345308999 345336275 5557076654 246118318 345334787 5553673224 553293370 553293389 553298398 553293362 345438353 1585670081 345323440 449208133 345333926 435 285 234 320 480 480 304 256 590 608 640 352 AUTHOR TITLE ISBN PAGES Isaac Azimov James Blish Larry Niven AUTHOR INSERT Author Master table Detail table 75 Understanding Normalization
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