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Cartesian Product
              The Cartesian product of two sets A and B, denoted by A × B, is the set of all ordered      A
              pairs where the first element is in A and the second element is in B. For example:
              A = {1,2,3} and B = {2,3}
              Then A x B = {(1,2), (1,3), (2,2), (2,3), (3,2), (3,3)}.




                            Brainy Fact


                    Set theory was created in 1874 by the German Mathematician Georg Cantor. Cantor defined infinite and well-
                    ordered sets and proved that there are more real numbers than natural numbers.






                      Introduction to Data Table Joins
              You must have noted by now that relational databases are based almost entirely upon set theory. Let us now study
              joins. A JOIN is used to combine rows from two or more tables, based on a related/common column between them.
              Joining tables is essentially a Cartesian product followed by a selection criterion.

              Different Types of Joins
              There are 4 types of joins:


              Inner Join
              When INNER JOIN keyword is used, those records are selected that have matching values
              in both the tables. In an inner join, only those tuples that satisfy the matching condition are   Left    Right
              included, while the remaining tuples are excluded.                                    Table       Table
              Syntax: SELECT table1.column1, table1.column2, table2.column1, .....

              FROM table1
              INNER JOIN table2
              ON table1.matching_column = table2.matching_column;
              where table1: First table, table2: Second table and matching_column: Column common to both the tables.


              Left Outer Join
              This join returns all records from the left table, and the matching records from the right
              table.                                                                                 Left       Right
              Syntax: SELECT table1.column1, table1.column2, table2.column1, ....                   Table       Table

              FROM table1
              LEFT JOIN table2
              ON table1.matching_column = table2.matching_column;

              Right Outer Join                                                                       Left       Right
              It returns all records from the right table, and the matching records from the left table.  Table  Table
              Syntax: SELECT table1.column1, table1.column2, table2.column1, ....

              FROM table1


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