Question

在尝试了解MySQL中的过程和游标如何工作时，我的代码一直遇到问题。我想让游标使用和/或更新代码中声明的变量，但是正确更新的唯一变量是var1和var2。
Cursor2应该只返回1个结果，但只返回空行，var3和var4不会更新-它们的值显然仍然是默认值。
与Cursor3和变量var4相同。

实际代码与此类似：

DELIMITER //

CREATE PROCEDURE nameProcedure()

proc_label:BEGIN
DECLARE finished INTEGER DEFAULT 0;
DECLARE var1 VARCHAR(20) DEFAULT "";
DECLARE var2 VARCHAR(30) DEFAULT "";
DECLARE var3 INT(3) DEFAULT 0;
DECLARE var4 int(3) DEFAULT 0;

 // first cursor, gives multiple rows as results 
DECLARE cursor1 CURSOR FOR
SELECT column1, column2
FROM table1;

 // second cursor, should give only 1 row as result 
DECLARE cursor2 CURSOR FOR
SELECT column1, column2 
FROM table2
WHERE column1=var1 
AND column2=var2;

 // third cursor, should give only 1 row as result 
DECLARE cursor3 CURSOR FOR 
SELECT count(column3) 
FROM table3 
WHERE column1=var3;

 // HANDLER 
DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1;

OPEN cursor1;
OPEN cursor2;
OPEN cursor3;

label: LOOP 

    FETCH cursor1 INTO var1, var2;

    IF finished=1 THEN LEAVE loop;
    END IF;

    FETCH cursor2 INTO var3, var4;

    IF finished=1 THEN LEAVE proc_label;
    END IF;

    FETCH cursor3 INTO var5;

    IF finished=1 THEN LEAVE proc_label;
    END IF;

    /* UPDATE some rows in tables using the values from var1, var2, var3, var4, var5 in WHERE clauses */

END LOOP loop;

CLOSE cursor1;

CLOSE cursor2;

CLOSE cursor3;

END//

我为这篇文章中的文字表示歉意，英语不是我的母语，并且我从未在论坛上发表过这篇文章，因此我不确定如何格式化它，以便使人们更容易理解这个问题。建议，更正等都非常受欢迎。

MySQL过程中的多个游标

0 个答案: