Page 176 - Artificial Intellegence_v2.0_Class_11
P. 176

Difference Operation
              The  difference  operation  removes  common  tuples  from  the  first  table.  The  set  operation  is  denoted  by  ‘–  ‘.  The
              expression (Student – Student 1) results is shown as:
                 Student                                                Student 1
                 Rollno     Name       Marks                             Rollno       Name       Marks
                  100      Prakash      256                                101        Vivek       256

                  102       Sudha       210                                103        Punit       269
                  103        Punit      269                                104       Kumar        287
                  105       Jimmy       210                                106        John        276

                  106        John       276

              Result of Difference Operation
                                                    Rollno      Name       Marks

                                                      100      Prakash      256
                                                      102       Sudha       210

                                                      105       Jimmy       210

              Cartesian Product Operation
              The cartesian product of two relations is the concatenation of tuples belonging to the two relations. The cartesian
              product is a binary operation and is denoted by (x). Consider the two relations as given below:
                 Student                                          Teacher
                  Rollno      Name                                      TNo.            TName

                   101         Vivek
                                                                         T01           Mr. Naveen
                   103         Punit                                     T02           Mr. Govind

                   106         John
              The cartesian product of the above two relations, Student x Teacher will produce the relation which has a degree (no.
              of columns) of 4 (2+2) and a cardinality (no. of rows) of 6 (3 x 2).
                                        Rollno       Name        TNo.             TName

                                         101         Vivek        T01           Mr. Naveen
                                         101         Vivek        T02           Mr. Govind

                                         103         Punit        T01           Mr. Naveen
                                         103         Punit        T02           Mr. Govind

                                         106         John         T01           Mr. Naveen
                                         106         John         T02           Mr. Govind


              Divide Operation
              Divide operation is used when we have to evaluate queries that contain the keyword ‘all’. For example:
                 • “Which persons have a bank account at ALL the banks in the city?”
                 • “Which students are registered on ALL the courses given by Shiva University?”

                 • “Which students are registered on ALL the courses that are taught in period 2?”

                    174     Touchpad Artificial Intelligence (Ver. 2.0)-XI
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