σ course = “Big Data” (STUDENT ) Studno Name Course Year cs1 Kannan Big Data II cs3 Lenin Big Data I PROJECT (symbol : Π ) The projection eliminates all attributes of the input relation but those mentioned in the projection list. The projection method defines a relation that contains a vertical subset of Relation. Example using Table . Π course (STUDENT) Result Course Big Data R language Python Programming duplicate row is removed in the result Note 12th Computer Chapter - - Database Concepts Example (using Table .
) Π studno, course (STUDENT) Result Studno Course cs1 Big Data cs2 R language cs3 Big Data cs4 Python Programming UNION (Symbol : ∪ ) It includes all tuples that are in tables A or in B. It also eliminates duplicates. Set A Union Set B would be expressed as A ∪ B Example Consider the following tables Table A Table B Studno Name Studno Name cs1 Kannan cs1 Kannan cs3 Lenin cs2 GowriShankar n cs4 Padmaja cs3 Lenin Table . Result Table A ∪ B Studno Name cs1 Kannan cs2 GowriShankar cs3 Lenin cs4 Padmaja SET DIFFERENCE ( Symbol : - ) The result of A – B, is a relation which includes all tuples that are in A but not in B.
The attribute name of A has to match with the attribute name in B. Example ( using Table . ) 12th Computer Chapter - - Result Table A - B cs4 Padmaja INTERSECTION (symbol : ∩ ) A ∩ B Defines a relation consisting of a set of all tuple that are in both in A and B. However, A and B must be union-compatible.
Example (using Table . ) A ∩ B cs1 Kannan cs3 Lenin PRODUCT OR CARTESIAN PRODUCT (Symbol : X ) Cross product is a way of combining two relations. The resulting relation contains, both relations being combined. A x B means A times B, where the relation A and B have different attributes.
This type of operation is helpful to merge columns from two relations. Table A Table A = Table B = Table A x B = x = Cartesian Product Fig. .