by Dinesh Thakur
Category: RDBMS

We have already seen relational algebra is a procedural language, in which user has to write the steps or procedure to obtain the required results but in general a user should not have to be concerned with the details of how to obtain information. In relational calculus user is not concerned with the procedure to obtain the results, he/she just tell his/her requirements and the output is available without knowing the method about its retrieval.

by Dinesh Thakur
Category: RDBMS

Relational operators are classified into two types:

• Traditional Set Operators

• Special Operators

by Dinesh Thakur
Category: RDBMS

Designing of database is most important responsibility of the software professionals who are dealing with the database related projects. For this they follow the Design Methodology. It helps the designer to plan, manage, control, and evaluate database development projects.

by Dinesh Thakur
Category: RDBMS

A relation is said to be in First Normal Form (lNF) if and only if every entry of the relation (the intersection of a tuple and a column) has at most a single value. In other words "a relation is in First Normal Form if and only if all underlying domains contain atomic values or single value only."

by Dinesh Thakur
Category: RDBMS

It deals with the cost of implementing locks depending upon the space and time. Here, space refers to data structure in DBMS for each lock and time refers to handling of lock request and release.

The cost of implementing locks depends on the size of data items. There are two types of lock granularity:

by Dinesh Thakur
Category: RDBMS

In order to understand deadlock, let us consider the following example:

by Dinesh Thakur
Category: RDBMS

A relation R is in Third Normal Form (3NF) if and only if the following conditions are satisfied simultaneously:

1. R is already in 2NF

2. No nonprime attribute is transitively dependent on the key. **Another way of expressing the conditions for Third Normal Form is as follows:**

1. R is already in 2NF

2. No nonprime attribute functionally determines any other nonprime attribute.

These two sets of conditions are equivalent.

As these two definitions of 3NF imply, the objective of transforming relations into 3NF is to remove all transitive dependencies. So, first we are going to explain the concept of transitive dependency.

by Dinesh Thakur
Category: RDBMS

Dr. E.F. Codd, the founder of the relational database systems, framed twelve rules to assist a database product to qualify as relational. An RDBMS product has to satisfy at least six of the 12 rules of Codd to be accepted as a full-fledged RDBMS. There is no RDBMS package commercially available that satisfies all the 12 rules. These rules are:

by Dinesh Thakur
Category: RDBMS

There are two approaches used in algorithms to deals with the problems of concurrency control. These are:

• Pessimistic Approach

• Optimistic Approach

by Dinesh Thakur
Category: RDBMS

Definition of second normal form is:

A relation R is in second normal form (2NF) if and only if it is in INF and very non-key attribute is fully dependent on the primary key.

About Dinesh Thakur

Dinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular Computer Notes blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.

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