MERGE JOIN (CARTESIAN)

Description

Performs a cartesian join between two tables

Versions

This operation is implemented in the following versions

7.3.4
8.0.4
8.0.5
8.0.6
8.1.5
8.1.6
8.1.7
9.0.1
9.2.0
10.1.0
10.2.0

Example

Note that at least one of the tables must be analyzed otherwise a NESTED LOOPS execution plan is executed.

This example was developed using Oracle 9.2.0.1 on Windows 2000

This example requires the following table definition 

    CREATE TABLE t1 (c1 NUMBER);
    CREATE TABLE t2 (c1 NUMBER);

The table does not need to be analysed

The statement

    SELECT t1.c1,t2.c1
    FROM t1,t2;

In Oracle 9.2 generates the following execution plan

0     SELECT STATEMENT Optimizer=CHOOSE
1   0   MERGE JOIN (CARTESIAN)
2   1     TABLE ACCESS (FULL) OF 'T1'
3   1     SORT (JOIN)
4   3       TABLE ACCESS (FULL) OF 'T2'

In Oracle 10.2 generates the following execution plan

0     SELECT STATEMENT Optimizer=CHOOSE
1   0   MERGE JOIN (CARTESIAN)
2   1     TABLE ACCESS (FULL) OF 'T1'
3   1     BUFFER (SORT)
4   3       TABLE ACCESS (FULL) OF 'T2'