【MySQL】游标的具体使用详解

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()//

运行结果：

mysql> call useCursor()//

+--------------------------------------+

| allName                              |

+--------------------------------------+

| f1;c3;c6;c5;c2;c4;c1;f1;f3;f4;f2;f5; |

+--------------------------------------+

1 row in set (0.00 sec)

While循环：

WHILE expression DO
Statements;
END WHILE
//实例
DECLARE num INT;
DECLARE my_string  VARCHAR(255);
SET num =1;
SET str ='';
WHILE num  < span>10DO
SET  my_string =CONCAT(my_string,num,',');
SET  num = num +1;
END WHILE;

loop循环游标：

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 ;

repeat循环游标：

/*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 ;

/*******************************************循环语句************************************************/
/*(1).WHILE循环*/
[ label: ]   WHILE  expression DO
statements
END   WHILE   [ label ] ;
/*(2).LOOP循环*/
[ label: ]  LOOP
statements
END  LOOP  [ label ] ;
/*(3).REPEAT UNTIL循环*/
[ label: ]  REPEAT
statements
UNTIL expression
END  REPEAT  [ label ] ;

原文地址：http://www.jb51.net/article/38317.htm