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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.
If the deletion violates referential integrity constraint, then three alternatives are available: Default option: - refuse the deletion. It is the job of the DBMS to describ
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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
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Attributes that are directly kept in the data base. For example, 'Birth date' attribute of a person. Derived Attributes that are not stored directly but can be derived
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Discuss the types of integrity constraints in which must be checked for the update operations - Insert and Delete. Give examples. Insert operation can violet any of the subse
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