rspec/rules/S2457/plsql/rule.adoc

== Why is this an issue?

A ``++CROSS JOIN++`` query will return all records where each row from the first table is combined with each row from the second table. This means that such a query returns the Cartesian product of the sets of rows from the joined tables, which is why it is also know as "Cartesian product query".


Such a query can return a huge amount of data, and therefore should be used only with great caution and only when really needed.


=== Noncompliant code example

[source,sql]
----
BEGIN
  -- Standard ANSI syntax
  SELECT *
    INTO employeeArray
    FROM employee CROSS JOIN department; -- Noncompliant; explicit cross join
END;
/

BEGIN
  -- Old syntax
  SELECT *
    INTO employeeArray
    FROM employee, department; -- Noncompliant; also a cross join
END;
/
----

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Remove this "CROSS JOIN" query


endif::env-github,rspecator-view[]