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Write short notes on relational model
The relational model uses a collection of tables to show both data and the relationships between those data. The relational model is an example of a record based model.
Views in relational algebra: 1. Basic expression contains either a) A relation in the database. b) A constant relation. 2. General expressions are madde out of sma
The database will enable college administrators the ability to track students initial major. This will help college officials decide how best to prepare students for their goals an
WHERE and HAVING clause in SQL ? The WHERE clause is commonly used for implementing conditions on each tuple of the relation. The HAVING clause is used in combination along wi
What is the need for triggers? Triggers are useful mechanisms for alerting humans or for starting particular tasks automatically when particular conditions are met.
data models are being replaced over years. Reasons and why does that happen?
Discuss the methods for a hash file to expand and shrink dynamically. What are the advantages and disadvantages of each? The hashing methods that permit dyanamic file expansi
Define the Immediate Update The immediate update methods may apply changes to the database on disk before the transaction arrives a successful conclusion. Though, these change
What is data definition language? Explain it in detail? The SQL DDL allows specification of not only a set of relations, but also information after each relation, containing
Example : Create a sequence named SEQSS that starts at 105, has a step of 1 and can take maximum value as 2000. CREATE SEQUENCE SEQSS START WITH 105 INCREMENT BY 1 MAX VA
To do the division operation R1 ÷ R2, R2 should be a correct subset of R1. In the following example R1 have attributes A and B and R2 have only attribute B so R2 is a correct subse
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