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Define Atom of domain relational calculus
An atom has the outline < x1, x2, ... , xn > -> r , in which r stands for a relation on n attributes and x1, x2, ... , xn are the domain variables or domain constraints.
x Θ y , in which x and y are domain variables and Θ is the comparison operator (<, >, <, >, =, ≠). It is needed that x and y have domains which can be compared by Θ.
x Θ c, in which x is a domain variable, Θ is a comparison operator, and c is a constraint in the domain of attributes for which x is a domain variable.
What is a recovery scheme? An integral part of a database system is a recovery scheme that can restore the database to the reliable state that existed before the failure.
Performance of Various Concurrency Control Mechanisms
DML Precompiler All the DBMS have two basic sets of Languages - Data Definition Language (DDL) that have the set of commands needed to define the format of the data that is b
Can a filed occur in several field groups. Yes. But it leads to redundant data redundancy.
Describe queries with complex types? The present extension of the SQL query language deal with the complex type Let us start with the simple example: Find the title and t
It defines that the tuple in one relation that refers to another relation must refer to an existing tuple in that relation. This constraint is states on two relations (not essentia
What is a guard condition? Explain it with a suitable example. The guard-condition is a Boolean expression written with respect to parameters of triggering event and attributes
ER diagram on cosmetics
The following relational database schema represents part of a simplified database used by a library: tblBook (BookID, Title, PublisherID, Category,Price) tblPublisher (Publishe
The ER diagram clearly showing the additional tables you have implemented. SQL table creation scripts for the tables you have set up. SQL scripts showing the sample data you
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