mysql-存储过程

1、数据存储：把多个sql语句封装成一个方法

注意：存储过程中的多游标：
     一个游标中可以存储多个字段，但是每个字段只能存储单个值，如果一个字段想要存储多个值,则只能对这个字段使用多游标。

BEGIN
declare m1 int DEFAULT 0;
declare m2 int DEFAULT 0;
DECLARE cursor1 CURSOR FOR SELECT maney FROM user_account WHERE card_id = id1;
declare cursor2 cursor for select maney from user_account where card_id = id2;
open cursor1;
fetch cursor1 into m1;
close cursor1;
open cursor2;
fetch cursor2 into m2;
close cursor2;
update user_account set maney = m1-tran where card_id = id1;
update user_account set maney = m2+tran where card_id = id2;
END

delimiter //    修改结束符
create procedure proc()
begin  
select * from student;
end
//
call  调用方法

变量的定义：
declare 变量名  type  default 默认值；
修改变量的值
set 变量名= 值 或 



Drop  procedure proc2;
delimiter //
Create procedure proc2()
Begin 
Declare var1 varchar(10) default null;
Declare var2 int  default 0;
select name ,age into  var1, var2 from student where id =1; 
         Result consisted of more than one row(这种错误出现的原因是没指定id 的值，结果多余变量的个数)
Select var1;
Select var2;
End  //
Delimiter ;


delimiter //
drop procedure if exists proc2;
Create procedure proc2()
Begin 
Declare var1 varchar(10) default null;
declare var2   int  default 0;
select name ,age into  var1, var2 from student where id =1; 
Select var1 as  姓名, var2 as 年龄;
End  //
Delimiter ;

1、存储过程：
Delimiter //    修改结束符
Drop  procedure if exists pro1;     判断，如果存在pro1 则删除
Create  procedure pro1()     创建 procedure 存储过程
Begin 
End//
Delimiter ;
Call pro1;



2、游标：

语法：
(
    声明游标
    declare cursor_name cursor for select_statement;
    打开游标（在使用游标之前）
    open cursor_name;
    获取游标中的数据 into 变量
    fetch cursor_name into var_name1,var_name2,...;
    关闭游标（在使用游标之后）
    close cursor_name;
)
 
 
 delimiter //
 drop procedure if exists pro;
 create procedure pro()
     begin
     declare var varchar(20) default null;
     declare cursor_name cursor for select name from student where id=1;
     open cursor_name;
     fetch cursor_name into var;
     close cursor_name;
     select var as 姓名;
     end //
 delimiter ;
 call pro;




procedure  程序、declare  声明、
delimiter //
Drop procedure if exists pro//
create procedure pro()
begin 
declare  var1  char(10) default null;
declare  var2  int  default 0;
declare  cursor1 cursor for select name ,age  from student where id=1;    
open cursor1;
fetch cursor1 into var1, var2;
close cursor1;
select var1 as ‘姓名’, var2 as ‘年龄’;
end  //
delimiter ;
call pro;




3、存储过程中的if判断语句

语法：
(
    if ..... then ......;
    else if ...... then ......;
    else .......;
    end if;
)


delimiter //
drop procedure if exists pro//
Create procedure pro()
begin 
declare var int;
if var is null then select 'var is null' as 结果;
Else select var as 结果;
end if;
Set var=10;
If var is null then select  'var is null' as 结果;
Else select var  as 结果;
End if;
End//
Delimiter ;
Call pro;


4、存储过程中的case判断语句

语法：
(
    case  要判断的变量
    when .... then .... ;
    when .... then .... ;
    ....;
    else ....;
    end case;
)


 delimiter //
 drop procedure if exists pro;
 create procedure pro()
     begin
     declare var int default 0;
     set var=5;
     case var
     when 1 then select * from student where id=var;
     when 2 then select * from student where id=var;
     when 3 then select * from student where id=var;
     else select 'no such case' as 结果;
     end case;
     end//
 delimiter ;
 call pro;
 
 
 
 5、存储过程中的loop循环语句
 
 语法：
 (
     loop sql_statement;
         if ... then leave/iterate;
         end if;
     end loop;
 )
 
 
 delimiter //
 drop procedure if exists pro//
 create procedure pro()
     begin
     declare var int default 0;
     myloop:loop insert student values(null,'Rose',var,'女');
          if var >=100 then leave myloop;
          end if;
          set var=var+1;
     end loop;
     end//
 delimiter ;
 call pro;
 
 注意：在sql语句中没有 “==”，直接用“=”来作为判断等于的符号。
 

 
 6、存储过程中的repeat循环语句
 
 语法：
 (
     repeat_label:repeat sql_statement;
     until ... end repeat repeat_label;
     
 )

 
 delimiter //
 select * from student//
 drop procedure if exists pro;
 create procedure pro()
 begin
 declare var int default 1;
 my_repeat:repeat insert into student values(null,'Rose',var,'女');
 set var=var+1;
 until var>100 end repeat my_repeat;
 end//
 delimiter ;
 call pro;
 select * from student;
 
 
 
 7、存储过程中的while循环
 
 语法：
 (
     while_label：while ...(循环条件)
     do sql_statement;
     end while while_label;
 )
 
 
 delimiter //
 select * from student//
 drop procedure if exists pro//
 create procedure pro()
 begin
 declare var int default 719;
 my_while:while var<=818
 do delete from student where id = var;
 set var=var+1;
 end while my_while;
 end//
 delimiter ;
 call pro;
 
 
 
 delimiter //
 drop procedure if exists pro//
 create procedure pro()
 begin
 declare var int default 1;
 my_while:while var<=100
 do insert into student values(null,'Rose',var,'女');
 set var=var+1;
 end while my_while;
 end//
 delimiter ;
 call pro;
 
 
 8、查看存储过程
 
 语法：
 (
     show {procedure/function} status [like 'pattern'];
     show create procedure pro_name;
 )
 
 show procedure status;
 show create procedure pro;
 
 
 
 9、修改存储过程
 
 
 10、删除存储过程
  语法：
  (
      drop {procedure/function} if exists pro_name;
  )
 
  drop procedure if exists pro;
 
 
 
  11、存储过程出错处理
  
  定义错误情况
  
  declare condition_name condition for condition_type;