PL/SQL Control Structures

`if-then-else`

if boolean_expression then
  sequence of statements;
[elsif boolean_expression then
  sequence of statements;]
[else
  sequence of statements;]
end if;

`case`

Ordinary `case` statement

casetest_variable
  when value_1 then sequence_of_statements_1;
  when value_2 then sequence_of_statements_2;
  ...
  when value_N then sequence_of_statements_N;
  [else else_sequence;]
 end case;

Labeled `case` statement

<<case_label>>
casetest_variable
  when value_1 then sequence_of_statements_1;
  when value_2 then sequence_of_statements_2;
  ...
  when value_N then sequence_of_statements_N;
  [else else_sequence;]
 end case case_label ;

Searched `case` statement

case
  when boolean_expression_1 then sequence_of_statements_1;
  when boolean_expression_1 then sequence_of_statements_2;
  ...
  when boolean_expression_1 then sequence_of_statements_N;
  [else else_sequence;]
 end case;

Simple `loop`

loop
  sequence_of_statements;
end loop;

This statements will loop forever. To exit of the loop we can use either the exit command:

loop
  if i < 10 then
    dbms_output.put_line('line number' || to_char(i));
  else
    exit;
  end if;
end loop;

or a conditional exit command

exit when boolean_condition;

`while` loop

while boolean_condition loop
  sequence_of_statements;
end loop;

`for` loop

for loop_counter in [reverse] low_bound..high_bound loop
  sequence_of_statements;
end loop;

where loop_counter is an implicitly declared index variable (you do not need to declare it, Oracle does it for you) and low_bound and high_bound specify the number of iterations. If the reverse keyword is present in the for loop, the loop index will iterates from the high value to the low value.

Labeling loops

Loops themselves can be labeled. If so, the labels can be used on the exit statement to indicate which loop to be exited:

<<outer_loop>>
for i in 1..10 loop
  dbms_output.put_line('Outer loop. Iteration #' || i);
  j := 0;
  <<inner_loop>>
  while j < i**2 loop
    dbms_output.put_line('Inner loop. Iteration #' || j);
    j := j + 1;
    exit outer_loop when j > 12;
  end loop inner_loop;
end loop outer_loop;