rspec/rules/S4062/plsql/rule.adoc

== Why is this an issue?

Oracle's ``++ROWNUM++`` is a pseudo column that numbers the rows in a result set. Unfortunately, it numbers the rows in the set _before_ ordering is applied. So combining the two in the same query won't get you the results you expect. Instead, you should move your selection and ordering into a subquery, and use ``++ROWNUM++`` only on the outer query.


=== Noncompliant code example

[source,sql]
----
SELECT fname, lname, deptId
FROM employee
WHERE rownum <= 10
ORDER BY salary  -- Noncompliant
----


=== Compliant solution

[source,sql]
----
SELECT * 
FROM ( SELECT fname, lname, deptId
    FROM employee
    ORDER BY salary
  )
WHERE rownum <= 10
----


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

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

=== Message

Order your results in a subquery and apply "rownum" at the level of the outer query.


=== Highlighting

* primary: order by
* secondary: rownum|row_number()


'''
== Comments And Links
(visible only on this page)

=== on 27 Jun 2017, 15:57:56 Pierre-Yves Nicolas wrote:
\[~ann.campbell.2] The title may be misleading. Some other possibilities: 

* "ROWNUM should not be used at the same query level as ORDER BY"
* or "ROWNUM should not be used with ORDER BY without a subquery"


=== on 27 Jun 2017, 16:09:55 Ann Campbell wrote:
\[~pierre-yves.nicolas]: "ORDER BY" should not be applied to queries that use "ROWNUM"

?

=== on 27 Jun 2017, 16:26:11 Pierre-Yves Nicolas wrote:
\[~ann.campbell.2] "ORDER BY should not be applied on top of a ROWNUM-based WHERE"? :)

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