Cross Join - (Oracle Joins)

A cross join in Oracle database is a join that returns the Cartesian product of two or more tables. It combines each row from one table with every row from the other table(s) to produce all possible combinations.

Syntax

SELECT column1, column2
FROM table1
CROSS JOIN table2;

Here, table1 and table2 are the names of the tables we want to join. column1 and column2 are the columns we want to select from each table.

Example

Consider the following two tables:

table1:

Id	Name
1	A
2	B
3	C

table2:

Id	Name
1	X
2	Y

To perform a cross join on these tables, we can use the following SQL statement:

SELECT table1.Name, table2.Name
FROM table1
CROSS JOIN table2;

The output of the query will be:

Name	Name
A	X
A	Y
B	X
B	Y
C	X
C	Y

Explanation

In the above example, we have used a cross join to combine each row from table1 with every row from table2 to produce all possible combinations. The resulting output is a table that contains all possible combinations of names from the two tables.

Use

A cross join is useful when we want to generate all possible combinations of rows between two or more tables. It can be used to generate test data, or when we want to compare every row from one table with every row from another table.

Important Points

• A cross join combines each row from one table with every row from the other table(s).
• It returns the Cartesian product of two or more tables.
• Cross joins can be used to generate test data or when we want to compare every row from one table with every row from another table.

Summary

In summary, a cross join in Oracle database is a join that returns the Cartesian product of two or more tables. It combines each row from one table with every row from the other table(s) to produce all possible combinations. Cross joins are useful when we want to generate all possible combinations of rows between tables. They are frequently used to generate test data, or when we want to compare every row from one table with every row from another table.