Selection And Projection Operation In Dbms Notes Aggregate Pdf

Author Dalbo 28 Jun 2026

There are two types of operations, selection that is used to filter rows in a table according to some conditions specified and projection that is used to transform rows in a table by selecting. Select can be used to list all of the row values or it can yield only those rows values. While selection operation works on rows, similarly projection operation of relational algebra works on columns

Selection and Projection operation - YouTube

Selection And Projection Operation In Dbms Notes Aggregate Pdf

It basically allows us to pick specific columns from a given relational table. Selection is also know as restrict, this operator yields values for all rows found in a table that satisfies given condition Selection and projection are two major basic model operations that are used when processing queries in dbms

Although both are associated with the operation of a database, it is used.

Both are fundamental in sql and nosql databases, but they serve different purposes Selection = rows, projection = columns You can (and often should) use them together to refine queries efficiently. The most common kind of select statement uses both selection and projection

A query of this kind returns some of the rows and some of the columns in a table, as the following figure shows. What is the difference between projection and selection Think of selection as finding the right people in a room, and projection as asking them for specific details (like their names or ages) Together, they help you extract precise, useful data from databases.

14. Query Optimization in DBMS | PPT

Herbalessence's answer is totally correct, but the basic idea is

With the selection operator you specify which rows you want, with the projection operator you specify which columns you want. Learn the difference between selection and projection in dbms with simple examples Understand how these operations filter rows and columns in sql.