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Dbms Assignment

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1. Identify and discuss the serious data redundancy problems exhibited by the file structure shown in Figure P1.5.

Answer:

Given the file's poor structure, the stage is set for multiple anomalies. For example, if the charge for JOB_CODE = EE changes from $85.00 to $90.00, that change must be made twice. Also, if employee June H. Sattlemeier is deleted from the file, you also lose information about the existence of her JOB_CODE = EE, its hourly charge of $85.00, and the PROJ_HOURS = 17.5. The loss of the PROJ_HOURS value will ultimately mean that the Coast project costs are not being charged properly, thus causing a loss of PROJ_HOURS*JOB_CHG_HOUR = 17.5 x $85.00 = $1,487.50 to the company.

Incidentally, note that the file contains different JOB_CHG_HOUR values for the same CT job code, thus illustrating the effect of changes in the hourly charge rate over time. The file structure appears to represent transactions that charge project hours to each project. However, the structure of this file makes it difficult to avoid update anomalies and it is not possible to determine whether a charge change is accurately reflected in each record. Ideally, a change in the hourly charge rate would be made in only one place and this change would then be passed on to the transaction based on the hourly charge. Such a structural change would ensure the historical accuracy of the transactions.

You might want to emphasize that the recommended changes require a lot of work in a file system.

FIGURE P1.5 The File Structure for Problems 1-4

2. Looking at the EMP_NAME and EMP_PHONE contents in Figure P1.5, what change(s) would you recommend?

Answer:

A good recommendation would be to make the data more atomic. That is, break up the data componnts whenever possible. For example, separate the EMP_NAME into its componenst EMP_FNAME, EMP_INITIAL, and EMP_LNAME.…...

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