1.游标

什么是游标，以及游标使用的相关语法。

#声明游标，存储查询结果集
#准备：创建表结构
#开启游标
#获取游标中的记录
#插入数据到新表中
#关闭游标
create procedure p11(in uage int)
begin
	declare uname varchar(100);
	declare upro varchar(100);
	declare u_cursor cursor for select name,profession from tb_user where age <= uage;
	
	drop table if exist tb_user_pro;
	create table if not exist tb_user_pro(
		id int primary key auto_increment,
		name varchar(100),
		profession varchar(100)
	);

	open u_cursor;
	while true do
		fetch u_cursor into uname,upro;
		insert into tb_user_pro values (null, uname, upro);
	end while;
	close u_cursor;
end;

call p11(40);

解决游标中如果没有数据了，跳出循环的问题。

SQLSTATE为sql状态码。可以用not found来代替

declare exit handler for not found close u_cursor;

create procedure p11(in uage int)
begin
	declare uname varchar(100);
	declare upro varchar(100);
	declare u_cursor cursor for select name,profession from tb_user where age <= uage;
	declare exit handler for SQLSTATE '02000' close u_cursor;
	
	drop table if exist tb_user_pro;
	create table if not exist tb_user_pro(
		id int primary key auto_increment,
		name varchar(100),
		profession varchar(100)
	);

	open u_cursor;
	while true do
		fetch u_cursor into uname,upro;
		insert into tb_user_pro values (null, uname, upro);
	end while;
	close u_cursor;
end;

call p11(40);