SQL中使用循環結構
解答 FOR,LOOP,WHILE,REPEAT是UDB/400的一種內部循環控制,用於遍歷表中符合條件的每一行記錄。
例如:
目的:更新employee庫,把所有北京籍員工的工資提高10%
例一:使用FOR循環
--------------------------------------------
CREATE
PROCEDURE QGPL/TEST_FOR
LANGUAGE SQL
BEGIN
FOR each_record
AS
---cur01 CURSOR FOR
------SELECT * FROM code,salary,city from employee
where city="Beijing"
------------UPDATE employee
------------SET salary=salary * 1.1
------------WHERE CURRENT OF cur01;
ENDFOR;
END;
例二:使用LOOP循環
----------------------------------------
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
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;
END;
例三:使用WHILE循環
---------------------------------------
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;
例四:使用REPEAT循環
------------------------------------------------
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;
SQL中使用循環結構