sql 四种循环结构，分别是：
FOR循环、LOOP循环、WHILE循环、REPEAT循环，可分别用于遍历表中符合条件的每一行记录。
sql server中没有for循环，不过可以用while来代替，具体请看：sql server for循环的问题。
下面为大家介绍一个案例，分别使用这四种循环来实现。
要求：更新employee库，把所有北京籍员工的工资提高10%，哈哈，北京的朋友有福了。
例1：使用FOR循环
例2：使用LOOP循环
CREATE PROCEDURE QGPL/TEST_LOOP
LANGUAGE SQL
BEGIN
DECLARE code_v char(10);
DECLARE salary_v integer;
DECLARE city_v char(20);
DECLARE C1 CURSOR FOR
---SELECT code,salary,city FROM employee WHERE city="Beijing";
OPEN C1;
loop_label:
LOOP
- FETCH C1 INTO code_v,salary_v,city_v;
--IF SQLCODE=0 THEN
------SET salary_v=salary_v*1.1;
------UPDATE employee SET salary=salary_v
---------WHERE CURRENT OF C1;
--ELSE
------LEAVE loop_label;
--END IF;
END LOOP loop_label;
CLOSE C1;
END;
例3：使用WHILE循环
CREATE PROCEDURE QGPL/TEST_WHILE
LANGUAGE SQL
BEGIN
DECLARE code_v char(10);
DECLARE salary_v integer;
DECLARE city_v char(20);
DECLARE at_end integer;
DECLARE C1 CURSOR FOR
---SELECT code,salary,city FROM employee WHERE city="Beijing";
OPEN C1;
SET at_end=0;
WHILE at_end = 0 DO
--FETCH C1 INTO code_v,salary_v,city_v;
--IF SQLCODE=0 THEN
------SET salary_v=salary_v*1.1;
------UPDATE employee SET salary=salary_v
---------WHERE CURRENT OF C1;
--ELSE
------SET at_end=1;
--END IF;
END WHILE;
CLOSE C1;
END;
例4：使用REPEAT循环
CREATE PROCEDURE QGPL/TEST_REPEAT
LANGUAGE SQL
BEGIN
DECLARE code_v char(10);
DECLARE salary_v integer;
DECLARE city_v char(20);
DECLARE C1 CURSOR FOR
---SELECT code,salary,city FROM employee WHERE city="Beijing";
OPEN C1;
repeat_label:
REPEAT
--FETCH C1 INTO code_v,salary_v,city_v;
--IF SQLCODE=0 THEN
------SET salary_v=salary_v*1.1;
------UPDATE employee SET salary=salary_v
---------WHERE CURRENT OF C1;
--END IF;
--UNTIL SQLCODE<>0;
END REPEAT repeat_loop;
CLOSE C1;
END;