mysql数据库中关于cursor游标的使用方法
　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 ;