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Explain the EXISTS and UNIQUE functions of SQL. Give an example for each?
EXISTS: The EXISTS function takes one parameter that is a SQL statement. If any records exist which match the criteria it returns true, or else it returns false. This provides you a clean, well-organized way to write a stored procedure in which does either an insert or update.
UNIQUE: If UNIQUE is particular then only unique values are used to compute the mean.
What are domain constraints? A domain is a set of values that might be assigned to an attribute .all values that appear in a column of a relation must be taken from the similar
How Relational Calculus is different from Relational Algebra? What do understand by TRC queries and DRC queries? Ans: Relational calculus contain two calculi, the tuple relati
The issues relating to the Design of the Physical Database Files Physical File is a file as stored on the disk. The major issues relating to physical files are: • Cons
What is the meaning of Data independence? Data independence means a programs that are not dependent on the physical attributes of data and a programs that are not dependent on
A customer places orders for parts and belongs to a particular industry group. An individual order is taken by a particular sales representative on a specific date and the sales re
What is the difference between internal tables and extract datasets? The lines of an internal table always have the similar structure. By using extract datasets, you can ha
It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records
Group By clauses • It is used to group database tuples on the basis of definite common attribute value like as employees of a department. WHERE clause still can be used
Improved performance: As the data is located near the site of its demand, and given the inherent parallelism because of multiple copies, speed of database access may be good for di
What is meant by data-transfer rate? The data-transfer rate is the rate at which data can be retrieved from or kept to the disk.
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