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What's the difference between a primary key and a unique key?
Both primary key and unique key enforces uniqueness of the column on which they are explained. But by default primary key creates a clustered index on the column, where are unique makes a no clustered index by default. Another main difference is that, primary key doesn't permit NULLs, but unique key permits one NULL only.
Explain Thomas' Write rule. Show how it is different from timestamp ordering protol Ans: In timestamp-based concurrency control the thomas Write rule is a rule. Given a Timest
What is meant by object identifiers? Object-oriented systems use an object identifier to recognize objects. Object identifiers are unique: that is every object has a single ide
what is meant semantic query optimization? how does it differ from other query optimization techniques?
Give short note on the following terms:Dirty pages and ETL a.) Dirty pages. These are buffer pages which comprise modifications which haven't been written to disk. b.
A use case diagram giving a pictorial overview of user requirements and brief use case descriptions. As the case study contains only an outline of a business scenario, you will als
What it creates while a primary key is combined with a foreign key? It creates Parent-Child relation ship between the tables that connect them while a primary key is combined w
Draw an ER diagram that shows the organization of a simple student database. The database captures the information about letter grades obtained by university students who enrolled
1. Which relational algebra operations do not need the participating tables to be union-compatible? Ans: Join is the relational algebra operations that do not need the particip
What is foreign key? A relation schema r1 derived from an ER schema may contain among its attributes the primary key of another relation schema r2.this attribute is known as a
A table joined with itself is called ? A table joined with itself is known as self join table. Normal 0 false false false EN-IN X-NONE X-NONE
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