PL/SQL 循环

----PL/SQL基本循环语句  LOOP
DECLARE 
   x number := 10; 
BEGIN 
   LOOP 
      dbms_output.put_line(x); 
      x := x + 10; 
      IF x > 50 THEN 
         exit; 
      END IF; 
   END LOOP; 
   -- after exit, control resumes here  
   dbms_output.put_line('After Exit x is: ' || x); 
END; 

-- 可以用 exit when 代替 exit
DECLARE 
   x number := 10; 
BEGIN 
   LOOP 
          exit WHEN x > 50; 
      dbms_output.put_line(x); 
      x := x + 10; 
     
   END LOOP; 
   -- after exit, control resumes here 
   dbms_output.put_line('After Exit x is: ' || x); 
END; 

 
---- while...loop
DECLARE 
   a number(2) := 10; 
BEGIN 
   WHILE a < 20 LOOP 
      dbms_output.put_line('value of a: ' || a); 
      a := a + 2;  --增量可以随意
   END LOOP; 
END; 

----for...loop 注意：增量只能是1
DECLARE 
   a number(2); 
BEGIN 
   FOR a in 10 .. 20 LOOP 
      dbms_output.put_line('value of a: ' || a); 
  END LOOP; 
END; 
---- 反转FOR LOOP语句
DECLARE 
   a number(2) ; 
BEGIN 
   FOR a IN REVERSE 10 .. 20 LOOP 
      dbms_output.put_line('value of a: ' || a); 
   END LOOP; 
END; 

-- 嵌套循环   求出2到100之间的素数 
DECLARE 
   i number(3); 
   j number(3); 
BEGIN 
   i := 2; 
   LOOP 
      j:= 2; 
      LOOP 
         exit WHEN ((mod(i, j) = 0) or (j = i)); 
         j := j +1; 
      END LOOP; 
   IF (j = i ) THEN 
      dbms_output.put_line(i || ' is prime'); 
   END IF; 
   i := i + 1; 
   exit WHEN i = 50; 
   END LOOP; 
END; 
-- 标记循环
DECLARE 
   i number(1); 
   j number(1); 
BEGIN 
   << outer_loop >> 
   FOR i IN 1..3 LOOP 
      << inner_loop >> 
      FOR j IN 1..3 LOOP 
         dbms_output.put_line('i is: '|| i || ' and j is: ' || j); 
      END loop inner_loop; 
   END loop outer_loop; 
END; 

--循环控制语句：continue
DECLARE 
   a number(2) := 10; 
BEGIN 
   -- while loop execution  
   WHILE a < 20 LOOP 
      dbms_output.put_line ('value of a: ' || a); 
      a := a + 1; 
      IF a = 15 THEN 
         -- skip the loop using the CONTINUE statement 
         a := a + 1; 
         CONTINUE; -- 之后的代码跳过，回到条件开始重新迭代
      END IF; 
   END LOOP; 
END; 
-- 循环控制语句：goto  不建议使用
DECLARE 
   a number(2) := 10; 
BEGIN 
   <<loopstart>> 
   -- while loop execution  
   WHILE a < 20 LOOP
   dbms_output.put_line ('value of a: ' || a); 
      a := a + 1; 
      IF a = 15 THEN 
         a := a + 1; 
         GOTO loopstart; 
      END IF; 
   END LOOP; 
END;