== Why is this an issue?

A ``++CASE++`` and a chain of ``++IF++``/``++ELSIF++`` statements is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to ``++true++``. 


Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it's simply dead code and at worst, it's a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior. 

=== Noncompliant code example

[source,sql]
----
IF param == 1 THEN
  x := 'A';
ELSIF param == 2 THEN
  x := 'B';
ELSIF param == 1 THEN -- Noncompliant, for sure this is a bug
  x := 'C';
END IF;

result := CASE param
   WHEN 1 THEN 'A'
   WHEN 2 THEN 'B'
   WHEN 1 THEN 'C'  -- Noncompliant
   ELSE 'D'
END;
----

=== Compliant solution

[source,sql]
----
IF param == 1 THEN
  result := 'A';
ELSIF param == 2 THEN
  result := 'B';
ELSIF param == 3 THEN
  result := 'C';
END IF;

result := CASE param
   WHEN 1 THEN 'A'
   WHEN 2 THEN 'B'
   WHEN 3 THEN 'C'
   ELSE 'D'
END;
----


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

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

include::../message.adoc[]

include::../highlighting.adoc[]

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

include::../comments-and-links.adoc[]

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