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
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
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;
