mysql 游标使用

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 ;