基于MySQL游标的具体使用详解

测试表 level ;

复制代码 代码如下:

create table test.level (name varchar(20));

代码

初始化

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drop procedure if exists useCursor //

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CREATE PROCEDURE useCursor()

BEGIN

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declare tmpName varchar(20) default '' ;
declare allName varchar(255) default '' ;
declare cur1 CURSOR FOR SELECT name FROM test.level ;

并设置 循环使用 变量 tmpname 为 null 跳出循环。

复制代码 代码如下:

declare CONTINUE HANDLER FOR SQLSTATE '02000' SET tmpname = null;

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OPEN cur1;

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FETCH cur1 INTO tmpName;

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WHILE ( tmpname is not null) DO
set tmpName = CONCAT(tmpName ,";") ;
set allName = CONCAT(allName ,tmpName) ;

复制代码 代码如下:

FETCH cur1 INTO tmpName;

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END WHILE;

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CLOSE cur1;

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select allName ;

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END;//

复制代码 代码如下:

call useCursor()//

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mysql> call useCursor()//

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

| allName|

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

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

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

1 row in set (0.00 sec)

复制代码 代码如下:

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 ;

复制代码 代码如下:

/*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 ;

复制代码 代码如下:

/*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 ;