MYSQL-5-存储过程

1. 变量

   1. 全局变量前有@@字符，由系统定义和维护

       select @@rowcount;--返回上一条语句执行的条数
       select @@version;--返回当前SQL Server服务器的日期版本和处理器类型
      

   2. 局部变量前有@字符，由用户定义和维护

2. 创建函数(了解)

    use school2;
    delimiter $$
    create function fun_get_sage(str varchar(12))
    returns char(12)
    begin
    	return(select sage from student where sname=str);
    end;
   

   调用：

    select fun_get_sage('李彤');
   

3. 存储过程

   1. 语句

       if...then...
       else if...then...
       else...
       end if;
      
       label:while... do
             
             end while;
       
       label:loop
             end loop;
      
       case
       when...then...
       when...then...
       else...
       end case;
      

   2. 实例一

       delimiter $$
       create procedure pro_test2()
       begin
       	select "ok";
       end $$
       
       call pro_test2();
      

   3. 实例二

       delimiter $$
       create procedure pro_test21(in n int)
       begin
       	select n*n;
       end $$
       
       call pro_test21(20);
      

   4. 实例三

       delimiter $$
       create procedure pro_test22(in n int,out m int)
       begin
       	set m=n*n;
       end $$
       
       set @a=30;
       set @b=0;
       call pro_test22(@a,@b);
       select @b;
      

   5. 实例四

       delimiter $$
       create procedure pro_test23(inout n int)
       begin
       	set n=n*n;
       end $$
       
       set @a=10;
       call pro_test23(@a);
       select @a;
      

   6. 删除一个学生

       delimiter $$
       create procedure pro_test24(in strname varchar(12))
       begin
       	declare num varchar(12) default '';
       	select sno into num from student where sname=strname;
       	delete from sc where sno=num;
       	delete from student where sno=num;
       	select '删除成功';
       end $$
       
       call pro_test24('大傻');
      

   7. 从0加到num

       delimiter $$
       create procedure pro_loop(inout num double)
       begin
       	declare total double default 0;
       	declare i int default 0;
       	while i<num do
       		set total=total+i;
       		set i=i+1;
       	end while;
       	set num=total;
       end $$
       
       set @n=100;
       call pro_loop(@n);
       select @n;
      

   8. 从0加到num，若和大于2000，则停止

       delimiter $$
       create procedure pro_loop2(inout num double)
       begin
       	declare total double default 0;
       	declare i int default 0;
       	
       	label:while i<num do
       					set total=total+i;
       					if total>2000 then
       							leave label;
       					end if;
       					set i=i+1;
       				end while;
       				set num = total;
       end $$
       
       set @n=100;
       call pro_loop2(@n);
       select @n;
      

   9. 查询 李大奎 c语言的成绩

       DELIMITER $$
       create  procedure pro_getGrade(in name VARCHAR(12),in cname VARCHAR(12),out res INT)
       COMMENT '查询成绩'
       BEGIN
       	DECLARE xuehao varchar(12) DEFAULT '';
       	DECLARE kehao varchar(12) DEFAULT '';
       
       	select sno into xuehao from student where sname=name limit 1;
       	select cno into kehao from course where cname=cname limit 1;
       	select grade into res from sc where sno=xuehao and cno=kehao;        
       END $$
      
       -- 调用：
       set @r = 0;
       call pro_getGrade('李大奎','c',@r);
       select @r;
      

   10. 分数每次增加num直到没有不及格的，当超过100，则为100

        delimiter $$
        create procedure pro_loop_add(in num int)
        begin
        	declare min_grade int default 0;
        	select min(grade) into min_grade from sc_copy;
        	label:while min_grade<60 do
        					update sc_copy set grade=grade+num;
        					select min(grade) into min_grade from sc_copy;
        				end while;
        	update sc_copy set grade=100 where grade>100;
        end $$
        
        -- 调用：
        call pro_loop_add(5);
       

来源：https://blog.csdn.net/qq_38328762/article/details/99167640