oracle 基础 控制机构+赋值

   --变量赋值
   declare
   identity :=0;
   a varchar2(59,0);
   b varchar2(50):='abc';
   a :='cba';
  
   -- 控制语句
   ----------------------------------
   if a>b then
       .........
   end if;
   ------------------------------------
   if a>b then
      .....
    else
       .....
    end if;
   -----------------------------------
   if a>b then
       ........
    elsif c>b then
       ........
    else
       ..........
    end if;
    -----------------------------------
    case variable
         when 'tt' then 'value1'
         when 'mm' then 'value2'
         when 'nn' then 'value3'
         else value4
    end;
    --------------------------------------
    while t<10000000 loop
        ........;
    end loop;
   
    --------------------------------------
    for 1_counter in 1-10
    loop
        statements;
    end loop;
    ---------------------------------------
     for 1_counter in reverse 1..10
    loop
        statements;
    end loop;