Introduction to SQL CROSS JOIN clause. What is Cross Join in SQL? What is Cross Join in Oracle? A cross join is a join operation that produces the Cartesian product of two or more tables. A Cross Join is also called as Cartesian Product, as it is a type of Join function that returns a result set by joining every row item of one table with each and every item of the other table.

Unlike other JOIN operators, it does not let you specify a join clause. To create a Cartesian product of tables in Oracle, you use the CROSS JOIN clause. The following illustrates the syntax of the CROSS JOIN clause: A cross join or Cartesian product is formed when every row from one table is joined to all rows in another. It normally happens when no matching join columns are specified.

Oracle Cross Join (Cartesian Products) The CROSS JOIN specifies that all rows from first table join with all of the rows of second table. If table A is cross joined with another table B, where table A has 10 records and table B has 10 records, the result set will have 100 records.

Oracle 中的JOIN1、概述1.1、所有的join连接，都可以加上类似where a.id=1000的条件，达到同样的效果。1.2、除了cross join不可以加on外，其它join连接都必须加上on关键字，后都可加where条件。1.3、虽然都可以加where条件，但是他们只在标准连接的结果集上查找where条件。 In Mathematics, given two sets A and B, the Cartesian product of A x B is the set of all ordered pair (a,b), which a belongs to A and b belongs to B. A CROSS JOIN is a JOIN operation that produces the Cartesian product of two tables. For example, with two sets A {x,y,z} and B {1,2,3}, the Cartesian product of A x B is the set of all ordered pairs (x,1), (x,2), (x,3), (y,1) (y,2), (y,3), (z,1), (z,2), (z,3). The CROSS JOIN clause produces the cross-product of two tables. Introduction to Oracle CROSS JOIN clause. Suppose, the source and target tables have four and three rows, respectively, a cross join between them results in (4 × 3 = 12) rows being returned provided by there is no WHERE clause have been applied … The SQL CROSS JOIN produces a result set which is the number of rows in the first table multiplied by the number of rows in the second table if no WHERE clause is used along with CROSS JOIN.This kind of result is called as Cartesian Product. If there are "x" rows in table1 and "y" rows in table2 then the cross join result set have x*y rows. Introduction to Oracle Cross Join. In Math, a Cartesian product is a mathematical operation that returns a product set of multiple sets. You may, however, specify a WHERE clause in the SELECT statement.

If WHERE clause is used with CROSS JOIN, it functions like an INNER JOIN.