【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 '' 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 ] ;

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