Facing syntax error in this simple code snippet

Question

select case
when to_number (to_char(sysdate,'mm')) < 7
then (to_number(to_char(sysdate,'yyyy')) - 1)
from dual
--while if in block works fine
declare
year number;
begin
year := to_number(to_char(sysdate,'yyyy'));
if (to_number(to_char(sysdate,'mm')) < 7) then
year := year - 1;
end if;
dbms_output.put_line('year = '|| year);
end;

Answer 1

You can have:
-- 1 case expression
-- 1.2 searched case expressions
-- 2 simple case statement
-- 2.1 searched case statement
In your case you need the first one(-- 1 case expression ), because you return an expression.
Indeed a simple case statement let you choose a sequence of PL/SQL statements to execute. This follows another syntax.
It's not always true this statements
In PL/SQL you would use "END CASE". For this reason I can quietly show you that I can even use 'case expression' in PL/SQL, without end case:
DECLARE
    subtype TTempWord is varchar2(20);         -- good notation :-)
    valToCompare constant tTempWord:='test';
    temp  tTempWord ;  
    temp2 tTempWord ;
    --- start locals-------     ;-)
    procedure Compare_Display  -- with no parameters just for this dummy test!
    is
    begin
      dbms_output.put_line('Word to compare:'||valToCompare); 
      dbms_output.put_line('temp:'||temp);
      dbms_output.put_line('temp2:'||nvl(temp2,'not assigned'));
      temp2:= case temp when valToCompare then 'identic ' else 'NOT identic' end ; -- I'm  not using *'END CASE'*
      dbms_output.put_line('    --- after the assignation --->');
      dbms_output.put_line('temp:'||temp);
      dbms_output.put_line('temp2:'||temp2);        
      dbms_output.new_line;dbms_output.new_line;
    end;
    --- end locals-------     ;-)
BEGIN
      temp:='testttt'; 
      Compare_Display ;
      temp:=valToCompare;
      temp2:='';
      Compare_Display ;
END;--output
Word to compare:test
temp:testttt
temp2:not assigned
    --- after the assignation --->
temp:testttt
temp2:NOT identic
Word to compare:test
temp:test
temp2:not assigned
    --- after the assignation --->
temp:test
temp2:identic
PS:for more explanations related to all the cases you could look for at http://tahiti.oracle.com/
Edited by: zep111 on Apr 28, 2011 11:25 AM