| Kirk Paul Lafler |
Joining two or more tables of data is a powerful feature in the relational model. The SQL procedure enables users to join
tables of information quickly and easily. Linking one piece of information with another piece of information is made
possible when at least one column is common to each table. This paper describes several join types including the
importance of joins, the difference between the various join types (inner and outer), the creation of outer (left, right, and
full) joins, the importance of the WHERE / ON clause(s) in creating and subsetting rows of data, the purpose of creating
and using table aliases to minimize the number of keystrokes, and the application of set operators. |