[英]How to properly write a cursor inside a function?
我需要你的幫助,因為我有點迷路了。 我試圖在谷歌上查看函數中的游標和關於這些的引用,但我似乎無法完全理解這個概念。 我有一個家庭作業,我需要:
這是我到目前為止所做的......
你能幫我解決提示的問題,或者至少是函數中游標的簡單示例/資源,這樣我就可以開始更好地掌握這個概念。
DROP FUNCTION IF EXISTS Program;
DELIMITER //
CREATE FUNCTION Program(IncSal DECIMAL(3,2))
RETURNS DECIMAL(8,2)
DETERMINISTIC
BEGIN
DECLARE Salaire DECIMAL (8,2);
DECLARE end BOOLEAN DEFAULT FALSE;
DECLARE CurSalary CURSOR FOR
SELECT Sala_EMPL
FROM EMPLOYE;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET end = TRUE;
OPEN CurSalary;
loop_cursor: LOOP
IF end THEN
LEAVE loop_cursor;
END IF;
UPDATE EMPLOYE
SET Sala_EMPL=(Sala_EMPL*IncSal);
END LOOP;
CLOSE CurSalary;
RETURN AVG(CurSalary);
END;
//
DELIMITER ;
If you use a cursor you have to FETCH from the cursor (please review https://dev.mysql.com/doc/refman/8.0/en/fetch.html ) without a fetch the loop is infinite. AVG 是一個聚合 function,您不能在 cursor 上進行 AVG(您需要 select..from)。 每次迭代 cursor 循環時,您的更新語句將適用於所有員工(邏輯上很荒謬)。 就我個人而言,我永遠不會使用 function,因為您嘗試做的事情在 function 中並不合適(我會使用程序)。
“工作”但錯誤的示例 function
DROP FUNCTION IF EXISTS f;
DELIMITER //
CREATE FUNCTION f(IncSal DECIMAL(3,2))
RETURNS DECIMAL(8,2)
DETERMINISTIC
BEGIN
DECLARE Salaire DECIMAL (8,2);
DECLARE end BOOLEAN DEFAULT FALSE;
DECLARE CurSalary CURSOR FOR
SELECT salary FROM EMPLOYEe;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET end = TRUE;
OPEN CurSalary;
loop_cursor: LOOP
fetch cursalary into salaire;
IF end THEN
LEAVE loop_cursor;
END IF;
UPDATE EMPLOYEe
SET Salary=salary + (salary*incsal);
END LOOP;
CLOSE CurSalary;
#RETURN AVG(CurSalary);
return (select avg(salary) from employee);
END;
//
DELIMITER ;
MariaDB [sandbox]> select * from employee;
+------------+-----------+--------------+--------+
| employeeid | firstname | departmentid | salary |
+------------+-----------+--------------+--------+
| 1 | aaa | 1 | 10000 |
| 2 | bbb | 2 | 10000 |
| 3 | ccc | 3 | 10000 |
+------------+-----------+--------------+--------+
3 rows in set (0.00 sec)
MariaDB [sandbox]>
MariaDB [sandbox]> select f(.05);
+----------+
| f(.05) |
+----------+
| 11576.00 |
+----------+
1 row in set (0.00 sec)
MariaDB [sandbox]>
MariaDB [sandbox]> select * from employee;
+------------+-----------+--------------+--------+
| employeeid | firstname | departmentid | salary |
+------------+-----------+--------------+--------+
| 1 | aaa | 1 | 11576 |
| 2 | bbb | 2 | 11576 |
| 3 | ccc | 3 | 11576 |
+------------+-----------+--------------+--------+
3 rows in set (0.00 sec)
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