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Define physical and logical data independence. How does this architecture help in achieving these?
Data independence entails that change in one view must not need a change in the view(s) above. There are two sorts of data independence: logical and physical. The meaning of Logical data independence is that the conceptual view can be changed without influencing the existing external view, that is a given record may be spilt or combined along with other records but the external views need not be modified to reflect this. The meaning of Physical data independence is that the physical storage structures or devices employed to store the data can be changed without effecting the existing conceptual view or external view, that is if earlier indexed sequential files are employed to store data and then the B- trees are used, even then the upper layers must not be effected.
For Colorado customers calculate the number of single products ordered. If a product is purchased on multiple orders, it should be counted only single time. The result should conta
Define multivalued dependency. What do understand by trivial multivalued dependency? Ans: A multivalued dependency is a full constraint among two sets of attributes in a rela
Dirty Reads: T10 reads a value which is updated by T9. This update has not been committed and T9 aborts. T9 T10 Value of x old value = 200
Explain the functions of data manager? Functions of Data Manager : - Convert operations in user's queries coming directly through query processor or indirectly in an applicatio
Write short notes on Schema diagram. A database schema along with primary key and foreign key dependencies can be depicted pictorially by schema diagram. Every relation appea
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Can we delete data element, which is being used by table fields. No we cant delete data element.
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Given the following relations TRAIN (NAME, START, DEST) TICKET (PNRNO., START, DEST, FARE) PASSENGER (NAME, ADDRESS, PNRNO.) Write SQL expressions for the following queries: No
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