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Explain how the object classes are mapped to tables.
Each object class maps to one or more than one tables in the database. The objects in the class may be partitioned horizontally or/and vertically. For instance, if class has many instances of which, a few are often referenced. In this case, horizontal partitioning may improve efficiency by placing the frequently accessed objects in a table, and the remaining objects in another tables. Similarly, if a class has attributes with different access patterns, it may help to partition the objects vertically.
What is transaction? Transaction is a unit of program implementation that accesses and possibly updated several data items.
What is the difference between a key and a superkey? Key - A key a single attribute or a combination of two or more attributes of an entity set which is used to identify one
3NF Normal Form A relation schema R is in 3NF if it is in 2NF and for each FD X A either of the following is true X is a Super-key of R. A is a prime attribute of R
About Attribute inheritance
Define physical image of a global relation at a site
Selective replication: This is a combination of generating small fragments of relation and replicating them rather than a entire relation. The data should be fragmented on require
Describe the two alternatives for specifying structural constraints on relationship kinds? Relationship kinds have certain constraints in which limit the possible combination o
What are the disadvantages of relational approach? Disadvantages of relational approach: • Substantial hardware and system software overhead • May not fit all business models •
Describe the capabilities offered via MySQL client APIs? . • Checking for errors. . • Connecting to the MySQL server, selecting a database, disconnecting from the server
Give two profit of Reuse of Code. Reusing the implementation . Place existing class directly inside a new class. The new class can be made up of any number and type of the oth
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