What is the difference between Select and Project Operations

sql select relational-algebra
gizgok picture gizgok · Mar 25, 2011 · Viewed 124.5k times · Source

I'm referring to the basic relational algebra operators here.
As I see it, everything that can be done with project can be done with select.

I don't know if there is a difference or a certain nuance that I've missed.

Answer

sgokhales picture sgokhales · Mar 25, 2011

Select Operation : This operation is used to select rows from a table (relation) that specifies a given logic, which is called as a predicate. The predicate is a user defined condition to select rows of user's choice.

Project Operation : If the user is interested in selecting the values of a few attributes, rather than selection all attributes of the Table (Relation), then one should go for PROJECT Operation.

See more : Relational Algebra and its operations

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