mysql数据库游标问题
【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 ] ;
