JOINs
The 1999 ANSI standard introduced complete JOIN syntax in the FROM clause. The prior method was to list the tables needed in the query in the FROM clause and then to define the joins between these tables in the WHERE clause. However, the conditions of the SQL statement are also listed in the WHERE clause. It was decided to enhance this syntax because listing of the joins and the conditions in the same WHERE clause can be confusing.
The 1999 ANSI join syntax includes cross joins, equijoins, full outer joins, and natural joins.
CROSS JOINs
The CROSS JOIN syntax indicates that you are creating a Cartesian product from two tables. The result set of a Cartesian product is usually meaningless, but it can be used to generate a lot of rows if ...
Get Oracle® PL/SQL® Interactive Workbook, Second Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
