Sri lanka web server - Figure 4-2: DELETE anomaly occurs when detail records
Figure 4-2: DELETE anomaly occurs when detail records removed without deleting master record first. . Update anomaly This anomaly is similar to deletion in that both master and detail records must be updated to avoid orphaned detail records. When cascading, ensure that any primary key updates are propagated to related child table foreign keys. Dependency, Determinants, and Other Jargon The following are some simple mathematical terms you should understand. . Functional dependency Y is functionally dependent on X if the value of Y is determined by X. In other words, if Y = X +1, the value of X will determine the resultant value of Y. Thus, Y is dependent on X as a function of the value of X. Figure 4-3 demonstrates functional dependency by showing that the currency being Pounds depends on the FXCODE value being GBP. . Determinant The determinant in the description of functional dependency in the previous point is X because X determines the value Y, at least partially because 1 is added to X as well. In Figure 4-3 the determinant of the currency being Deutsche Marks is that the value of FXCODE be DM. The determinant is thus FXCODE. 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 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 Master table Detail table Delete detail records first to avoid an anomaly 76 Chapter 4
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