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What is NULL? Give an example to described testing for NULL in SQL?
The NULL SQL keyword is used to represent either a missing value or a value which is not applicable in a relational table. Consider there is a relation:
Person(id, name, address, phone)Now to search ids and names of person who do not have a phone is: Select id, name from Person where phone is null
Explain weak and strong entity type ? Weak and Strong entity type: An entity set which does not have a primary key is referred to as a weak entity set. The existence of a wea
The physical location of a record is determined by which mathematical formula that transforms a file key into a record location? The physical location of a record is determined
we need example of 2phase locking
Define blocks? The database system resides eternally on non-volatile storage, and is into fixed-length storage units known as blocks.
triggering
What is conceptual schema? The schemas at the view level are known as subschema that describe dissimilar views of the database.
Define the phases of two phase locking protocol Growing phase: a transaction may get locks but not release any lock. Shrinking phase: a transaction might be release locks bu
What are referential integrity constraints? A value that appears in single relation for a given set of attributes also appears for a particular set of attributes in another rel
What is the archtetype/instance pattern? The archetype/instance pattern happens when one entity tracks occurrences of another entity. A common example is the relationship among
Explain the Weak Entity Set An Entity set which does not have sufficient attribute to make a primay key is known as weak entity set. For instance, dependents of an employee in
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