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Update Operations and Dealing with Constraint Violations
There are three basic operations to be executes on relations:
The INSERT Operation:
The insert operation permits us to insert a new tuple in a relation. When we try to insert a new record, then any of the following four types of constraints can be violated:
• Entity Integrity constraint: If the primary key attribute value of new tuple t is given as null.
discuss the purpose of the concurrency control?
What is Index? An index is a physical structure having pointers to the data. Indices are created in an existing table to locate rows more quickly and efficiently. It is possibl
Define seek time. The time for repositioning the arm is known as the seek time and it enhances with the distance that the arm is known as the seek time.
Example :; transfers transfer_amount from x's account to y's account ; Supposes x&y both accounts exist TRANSACTION (x, y, transfer_amount) Start transaction IF X AND Y
Define average seek time. The average seek time is the average of the seek times, calculated over a sequence of random requests.
What are the failures of Controlling Events Between Objects Failure Unintentional termination of system. Several possible causes: failure of system hardware, o
What is transaction? Transaction is a unit of program implementation that accesses and possibly updated several data items.
Databases and data warehouses both are databases and both contains number of rows and columns of tables containing data. Data warehouse is really different from databases because d
A domain is a set of permissible values that can be given to an attribute. So each attribute in a table has a definite domain. Values to these attributes cannot be assigned outside
A database to track your progress in your college program will track your progress towards graduation! A database that has information containing the classes that you have taken, c
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