mysql 游标使用

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请使用 mysql 1.5 或以上version;

测试表 level ;

create table test.level (name varchar(20));

再 insert 些数据 ;

代码 Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> /*初始化*/  drop procedure if exists  useCursor //     /*建立 存储过程 create */  CREATE PROCEDURE useCursor()    BEGIN    /*局部变量的定义 declare*/          declare tmpName varchar(20) default '' ;         declare allName varchar(255) default '' ;         declare cur1 CURSOR FOR SELECT name FROM test.level ;         /*    mysql 不知道为什么用异常加入判断 ？          *    此请参考官方文档 20.2.11. 光标 光标           *        这把 游标 异常后 捕捉           *        并设置 循环使用 变量 tmpname 为 null 跳出循环。          */         declare CONTINUE HANDLER FOR SQLSTATE '02000' SET tmpname = null;      /*开游标*/      OPEN cur1;         /*游标向下走一步*/          FETCH cur1 INTO tmpName;         /* 循环体 这很明显 把游标查询出的 name 都加起并用 ; 号隔开 */      WHILE ( tmpname is not null) DO          set tmpName = CONCAT(tmpName ,";") ;          set allName = CONCAT(allName ,tmpName) ;        /*游标向下走一步*/         FETCH cur1 INTO tmpName;      END WHILE;      CLOSE cur1;    select allName ;END;//call useCursor()//

运行结果：

代码 Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->mysql> call useCursor()//+--------------------------------------+| allName                              |+--------------------------------------+| f1;c3;c6;c5;c2;c4;c1;f1;f3;f4;f2;f5; |+--------------------------------------+ row in set (0.00 sec)

代码 Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->DELIMITER $$    DROP PROCEDURE IF EXITS cursor_example$$  CREATE PROCEDURE cursor_example()       READS SQL DATA  BEGIN       DECLARE l_employee_id INT;       DECLARE l_salary NUMERIC(8,2);       DECLARE l_department_id INT;       DECLARE done INT DEFAULT 0;       DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees;       DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;         OPEN cur1;       emp_loop: LOOP           FETCH cur1 INTO l_employee_id, l_salary, l_department_id;           IF done=1 THEN               LEAVE emp_loop;           END IF;       END LOOP emp_loop;       CLOSE cur1;  END$$  DELIMITER ;

代码Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->/*创建过程*/DELIMITER //DROP PROCEDURE IF EXISTS test //CREATE PROCEDURE test()BEGIN    DECLARE done INT DEFAULT 0;    DECLARE a VARCHAR(200) DEFAULT '';    DECLARE c VARCHAR(200) DEFAULT '';        DECLARE mycursor CURSOR FOR SELECT  fusername FROM uchome_friend;    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;        OPEN mycursor;        REPEAT         FETCH mycursor INTO a;        IF NOT done THEN            SET c=CONCAT(c,a);/*字符串相加*/        END IF;            UNTIL done END REPEAT;        CLOSE mycursor;        SELECT c;END //DELIMITER ;