(SQL) Join

Joins are wasy to combine tabular data tables together to produce an output of tabular data to find information we might need in the database.

There are different types of joins:

?Inner join (produces intersection between two tables)
?Cross join (produces Cathesian product of two tables)
?Left join (produces table that contains the left table and the intersection of the right table. If the intersection does not exists, the right table part is set to NULL)
?Left join (produces table that contains the right table and the intersection of the left table. If the intersection does not exists, the left table part is set to NULL)

Inner joins are symmetrical in that the same rows from each table are returned in the final resultset, if no match is found in all tables joined that row is excluded in the resultset that is returned. Outer joins include all rows at the border of the join whether or not matches are found in each table.

last edited (October 23, 2006) by bilderbikkel, Number of views: 1063, Current Rev: 2 (Diff)

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