MySQL游标使用实例分享

#测试表 level ;
create table test.level (name varchar(20));

#再 insert 些数据 ;
#代码 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 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MySQL 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;

#结束循环体:
END WHILE;

#关闭游标
CLOSE cur1;

#选择数据
select allName ;

#结束存储过程
END;//

调用存储过程：
call useCursor()//

mysql> call useCursor()//
+--------------------------------------+
| allName                              |
+--------------------------------------+
| f1;c3;c6;c5;c2;c4;c1;f1;f3;f4;f2;f5; |
+--------------------------------------+
1 row in set (0.00 sec)

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 ; 

/*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 ;