【MySQL】游標的具體使用詳解

測試表 level ;

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

再 insert 些數據 ;代碼,初始化

drop procedure if exists useCursor //

建立 存儲過程 create

CREATE PROCEDURE useCursor()
BEGIN

局部變量的定義 declare

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

MySQL 游標 異常后 捕捉

並設置 循環使用 變量 tmpname 為 null 跳出循環。

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

開游標

OPEN cur1;

游標向下走一步

FETCH cur1 INTO tmpName;

循環體 這很明顯 把MySQL 游標查詢出的 name 都加起並用 ; 號隔開

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

游標向下走一步

FETCH cur1 INTO tmpName;

結束循環體:

END WHILE;

關閉游標

CLOSE cur1;

選擇數據

select allName ;

結束存儲過程

END;//

調用存儲過程：

call useCursor()//

運行結果：

mysql> call useCursor()//

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

| allName                              |

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

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

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

1 row in set (0.00 sec)

While循環：

WHILE expression DO
    Statements;
END WHILE
//實例
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循環游標：

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循環游標：

/*創建過程*/
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 ;

/*******************************************循環語句************************************************/
/*(1).WHILE循環*/
 [ label: ]   WHILE  expression DO
 statements
 END   WHILE   [ label ] ;
/*(2).LOOP循環*/
 [ label: ]  LOOP
  statements
  END  LOOP  [ label ] ;
/*(3).REPEAT UNTIL循環*/
 [ label: ]  REPEAT
 statements
 UNTIL expression
 END  REPEAT  [ label ] ;

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