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Explain retrieval in QBE?
Retrieval in QBE : A "GUI" for expressing queries.
But has influenced many projects Especially PC Databases: Paradox, Access, etc.
How does Tuple-oriented relational calculus vary from domain-oriented relational calculus? The tuple-oriented calculus uses a tuple variables i.e., variable whose only allowed
Compute the closure (F+) for the following set of the functional dependencies defined on R(a,b,c,d), where F - {c→ a, ab → d, a → b, d → c}, i.e. what are all of the FDs implied b
Multiple column Queries: Syntax: SELECT COLUMN1, COL2,...... FROM TABLE WHERE (COLUMN1, COL2, ...) IN (SELECT COLUMN1, COL2,.... FROM TABLE WHERE );
non numeric literals
In tuple relational calculus P1 → P2 is equivalent to ? A In tuple relational calculus P1→ P2 is equivalent to ¬P1 V P2. (The logical implication expression A B, meaning
What is foreign key? Foreign Key - Let there are two relations in tables R and S. Any candidate key of the relation R that is referred in the relation S is known as the forei
A basic model of Database Access Control Models of database access control have grown out of previous work on protection in operating systems. Let us talk about one simple mode
Sequences Sequences: Automatically produce unique numbers Are sharable Are typically used to make a primary key value Replace application code Speed up t
Define union compatibility? Explain why INTERSECTION of two relations cannot be performed if they are not union compatible? Two relations R(A1, A2,-------, An) and S(B1, B2,--
Data Redundancy -A lot of information is being repeated in the relation. For instance, the information that MCS-014 is named SSAD is repetitive, address of Rahul is "D- 27, Main ro
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