mysql数据库中关于Cursor游标的使用方法_MySQL

　DECLARE cursor_name CURSOR FOR SELECT_statement;

　　游标操作

　　OPEN 打开游标

　　OPEN cursor_name;

　　FETCH 获取游标当前指针的记录，并传给指定变量列表,注意变量数必须与MySQL游标返回的字段数一致,要获得多行数据，使用循环语句去执行FETCH

　　FETCH cursor_name INTO variable list;

　　CLOSE关闭游标

　　CLOSE cursor_name ;

　　注意:MySQL的游标是向前只读的,也就是说，你只能顺序地从开始往后读取结果集，不能从后往前，也不能直接跳到中间的记录

open 打开实例

mysql>
mysql> CREATE TABLE Employee(
-> id int,
-> first_name VARCHAR(15),
-> last_name VARCHAR(15),
-> start_date DATE,
-> end_date DATE,
-> salary FLOAT(8,2),
-> city VARCHAR(10),
-> description VARCHAR(15)
-> );
Query OK, 0 rows affected (0.02 sec)

mysql>
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values (1,'Jason', 'Martin', '19960725', '20060725', 1234.56, 'Toronto', 'Programmer');
Query OK, 1 row affected (0.01 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(2,'Alison', 'Mathews', '19760321', '19860221', 6661.78, 'Vancouver','Tester');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(3,'James', 'Smith', '19781212', '19900315', 6544.78, 'Vancouver','Tester');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(4,'Celia', 'Rice', '19821024', '19990421', 2344.78, 'Vancouver','Manager');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(5,'Robert', 'Black', '19840115', '19980808', 2334.78, 'Vancouver','Tester');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(6,'Linda', 'Green', '19870730', '19960104', 4322.78,'New York', 'Tester');
Query OK, 1 row affected (0.01 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(7,'David', 'Larry', '19901231', '19980212', 7897.78,'New York', 'Manager');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(8,'James', 'Cat', '19960917', '20020415', 1232.78,'Vancouver', 'Tester');
Query OK, 1 row affected (0.00 sec)

mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id | first_name | last_name | start_date | end_date | salary | city | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| 1 | Jason | Martin | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto | Programmer |
| 2 | Alison | Mathews | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester |
| 3 | James | Smith | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester |
| 4 | Celia | Rice | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager |
| 5 | Robert | Black | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester |
| 6 | Linda | Green | 1987-07-30 | 1996-01-04 | 4322.78 | New York | Tester |
| 7 | David | Larry | 1990-12-31 | 1998-02-12 | 7897.78 | New York | Manager |
| 8 | James | Cat | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.02 sec)

mysql>
mysql>
mysql>
mysql>
mysql> DELIMITER //www.3ppt.com
mysql> CREATE FUNCTION city_list() RETURNS VARCHAR(255)
-> BEGIN
->
-> DECLARE finished INTEGER DEFAULT 0;
-> DECLARE city_name VARCHAR(50) DEFAULT "";
-> DECLARE list VARCHAR(255) DEFAULT "";
-> DECLARE city_cur CURSOR FOR SELECT city FROM employee;
-> DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1;
->
-> OPEN city_cur;
->
-> get_city: LOOP
-> FETCH city_cur INTO city_name;
-> IF finished THEN
-> LEAVE get_city;
-> END IF;
-> SET list = CONCAT(list,", ",city_name);
-> END LOOP get_city;
->
-> CLOSE city_cur;
->
-> RETURN SUBSTR(list,3);
-> END
-> //
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER ;
mysql>
mysql> SELECT city_list() AS cities;
+------------------------------------------------------------------------------------+
| cities |
+------------------------------------------------------------------------------------+
| Toronto, Vancouver, Vancouver, Vancouver, Vancouver, New York, New York, Vancouver |
+------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql>
mysql> drop function city_list;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)

========
游标的Handler

mysql> DELIMITER //
mysql> CREATE FUNCTION city_list() RETURNS VARCHAR(255)
-> BEGIN
->
-> DECLARE finished INTEGER DEFAULT 0;
-> DECLARE city_name VARCHAR(50) DEFAULT "";
-> DECLARE list VARCHAR(255) DEFAULT "";
-> DECLARE city_cur CURSOR FOR SELECT city FROM employee;
-> DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1;
->
-> OPEN city_cur;
->
-> get_city: LOOP
-> FETCH city_cur INTO city_name;
-> IF finished THEN
-> LEAVE get_city;
-> END IF;
-> SET list = CONCAT(list,", ",city_name);
-> END LOOP get_city;
->
-> CLOSE city_cur;
->
-> RETURN SUBSTR(list,3);
-> END
-> //
Query OK, 0 rows affected (0.00 sec)

mysql> DELIMITER ;
mysql>
mysql> SELECT city_list() AS cities;
+------------------------------------------------------------------------------------+
| cities |
+------------------------------------------------------------------------------------+
| Toronto, Vancouver, Vancouver, Vancouver, Vancouver, New York, New York, Vancouver |
+------------------------------------------------------------------------------------+
1 row in set (0.02 sec)

mysql>
mysql> drop function city_list;
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
====

mysql 游标数据输出实例

mysql> delimiter $$
mysql> CREATE PROCEDURE myProc()
-> READS SQL DATA
-> BEGIN
-> DECLARE l_last_row INT DEFAULT 0;
-> DECLARE l_dept_id INT;
-> DECLARE c_dept CURSOR FOR
-> SELECT id
-> FROM employee;
-> /* handler to set l_last_row=1 if a cursor returns no more rows */
-> DECLARE continue handler for NOT FOUND SET l_last_row=1;
->
-> OPEN c_dept;
-> dept_cursor: LOOP
-> FETCH c_dept INTO l_dept_id;
-> IF (l_last_row=1) THEN
-> LEAVE dept_cursor;
-> END IF;
-> select l_dept_id;
->
-> END LOOP dept_cursor;
-> CLOSE c_dept;
->
-> END$$
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> delimiter ;