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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 or more examples (rows) of the set (table). It is a minimal combination of attributes.
Super Key - A super key is a set of one or more attributes in which, taken collectively, permits us to identify uniquely a tuple within the relation.
What are object interaction diagrams? Object interaction diagrams are the diagrams that used to describe order in which messages are communicated in execution of an operation,
What is Message switching Message switching transmits data units which can be arbitrarily long. Packet switching has a utmost packet size, if any message longer than that, it s
Describe relational model? Structure of relational data base Basic structure Database schema Keys Schema diagram Query languages
What are the physical characteristics of magnetic disks? Ans: A magnetic disk is a circular plate or platter of plastic or metal that is coated with magnetizable material lik
Types of Locks There are two necessary types of locks: Binary lock : This locking mechanism has two states for to a data item: locked or unlocked Multiple-mode loc
Define multivalued dependency and 4NF. Ans: Multivalued Dependency - Assume R be a relation schema and let α ⊆ R and β ⊆ R. The multivalued dependency α →→β holds o
Define the following constraints for the table client. (i) BAL_DUE must be at least 1000. (ii) NAME is a unique key. (i)ALTER TABLE CLIENT ADD CONSTRAINT CLIENT_BAL_DUE_C1
Define the terms i) DDL ii) DML DDL: Data base schema is particular by a set of definitions expressed by a special language known as a data definition language. DML: A data
Scenario 1: Power goes out after the first instruction. What happens?
The Update Operations : Update operations are used for altering database values. The constraint violations faced by this operation are logically the similar as the problem faced
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