CREATE TABLE IF NOT EXISTS `store` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`count` int(11) NOT NULL DEFAULT '1',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=7;
INSERT INTO `store` (`id`, `name`, `count`) VALUES
(1, 'android', 15),
(2, 'iphone', 14),
(3, 'iphone', 20),
(4, 'android', 5),
(5, 'android', 13),
(6, 'iphone', 13);
我们现在要用存储过程做一个功能，统计iphone的总库存是多少，并把总数输出到控制台 。
--在windows系统中写存储过程时，如果需要使用declare声明变量，需要添加这个关键字，否则会报错 。
delimiter //
drop procedure if exists StatisticStore;
CREATE PROCEDURE StatisticStore()
BEGIN
--创建接收游标数据的变量
declare c int;
declare n varchar(20);
--创建总数变量
declare total int default 0;
--创建结束标志变量
declare done int default false;
--创建游标
declare cur cursor for select name,count from store where name = 'iphone';
--指定游标循环结束时的返回值
declare continue HANDLER for not found set done = true;
--设置初始值
set total = 0;
--打开游标
open cur;
--开始循环游标里的数据
read_loop:loop
--根据游标当前指向的一条数据
fetch cur into n,c;
--判断游标的循环是否结束
if done then
leave read_loop; --跳出游标循环
end if;
--获取一条数据时，将count值进行累加操作，这里可以做任意你想做的操作，
set total = total + c;
--结束游标循环
end loop;
--关闭游标
close cur;
--输出结果
select total;
END;
--调用存储过程
call StatisticStore();
drop procedure if exists StatisticStore1;
CREATE PROCEDURE StatisticStore1()
BEGIN
declare c int;
declare n varchar(20);
declare total int default 0;
declare done int default false;
declare cur cursor for select name,count from store where name = 'iphone';
declare continue HANDLER for not found set done = true;
set total = 0;
open cur;
fetch cur into n,c;
while(not done) do
set total = total + c;
fetch cur into n,c;
end while;
close cur;
select total;
END;
call StatisticStore1();
drop procedure if exists StatisticStore2;
CREATE PROCEDURE StatisticStore2()
BEGIN
declare c int;
declare n varchar(20);
declare total int default 0;
declare done int default false;
declare cur cursor for select name,count from store where name = 'iphone';
declare continue HANDLER for not found set done = true;
set total = 0;
open cur;
repeat
fetch cur into n,c;
if not done then
set total = total + c;
end if;
until done end repeat;
close cur;
select total;
END;
call StatisticStore2();
游标嵌套
在mysql中，每个begin end 块都是一个独立的scope区域，由于MySql中同一个error的事件只能定义一次，如果多定义的话在编译时会提示Duplicate handler declared in the same block 。
drop procedure if exists StatisticStore3;
CREATE PROCEDURE StatisticStore3()
BEGIN
declare _n varchar(20);
declare done int default false;
declare cur cursor for select name from store group by name;
declare continue HANDLER for not found set done = true;
open cur;
read_loop:loop
fetch cur into _n;
if done then
leave read_loop;
end if;
begin
declare c int;
declare n varchar(20);
declare total int default 0;
declare done int default false;
declare cur cursor for select name,count from store where name = 'iphone';
declare continue HANDLER for not found set done = true;
set total = 0;
open cur;
iphone_loop:loop
fetch cur into n,c;
if done then
leave iphone_loop;
end if;
set total = total + c;
end loop;
close cur;
select _n,n,total;
end;
begin
declare c int;
declare n varchar(20);
declare total int default 0;
declare done int default false;
declare cur cursor for select name,count from store where name = 'android';
declare continue HANDLER for not found set done = true;
set total = 0;
open cur;
android_loop:loop
fetch cur into n,c;
if done then
leave android_loop;
end if;
set total = total + c;
end loop;
close cur;
select _n,n,total;
end;
begin
end;
end loop;
close cur;
END;
call StatisticStore3();
上面就是实现一个嵌套循环，当然这个例子比较牵强 。凑合看看就行 。 。
动态SQL
Mysql 支持动态SQL的功能，
set @sqlStr='select * from table where condition1 = ?';
prepare s1 for @sqlStr;
--如果有多个参数用逗号分隔
execute s1 using @condition1;
--手工释放，或者是 connection 关闭时， server 自动回收
deallocate prepare s1;
