MySQL存储过程概念、原理与常见用法详解

create procedure procedureName()
begin
  //--sql 语句
end$

show procedure status

drop procedure procedureName;

call procedureName();

create procedure p1()
begin
  select 2+3;
end$

call p1();

create procedure p2()
begin
  declare age int default 18;
  declare height int default 180;
  select concat('年龄：',age,'身高：',height);
end$

create procedure p3()
begin
  declare age int default 18;
  set age := age + 20;
  select concat('20年后年龄：',age);
end$

if condition then
  statement
elseif
  statement
else
  statement
end if;

create procedure p4()
begin
  declare age int default 18;
  if age >= 18 then
  select '已成年';
  else
  select '未成年';
  end if;
end$

create procedure p5(width int,height int)
begin
  select concat('你的面积是：',width * height) as area;
  if width > height then
    select '你比较胖';
  elseif width < height then
    select '你比较瘦';
  else
  select '你比较方';
  end if;
end$

create procedure p6()
begin
  declare total int default 0;
  declare num int default 0;
  while num <= 100 do
    set total := total + num;
    set num := num + 1;
  end while;
  select total;
end$

create procedure p7(in n int)
begin
  declare total int default 0;
  declare num int default 0;
  while num <= n do
    set total := total + num;
    set num := num + 1;
  end while;
  select total;
end$

call p7(100);

create procedure p8(in n int,out total int)
begin
  declare num int default 0;
  set total := 0;
  while num <= n do
    set total := total + num;
    set num := num + 1;
  end while;
end$

call p8(100,@total); --100为输入型参数，而@total为输出型变量
select @total; --输出@total变量

create procedure p9(inout age int)
begin
  set age := age+20;
end$

set @age = 18; --设置@age变量为18
call p9(@age); --调用p9存储过程，@age变量为实参
select @age; --显示@age变量

create procedure p10()
begin
  declare pos int default 0;
  set pos := floor(5*rand());
  case pos
  when 1 then select '仍然在飞';
  when 2 then select '落在海里';
  when 3 then select '落在陆上';
  else select '我不知道在哪里';
  end case;
end$

[begin_label:] REPEAT
  statement_list
UNTIL search_condition
END REPEAT [end_label]

create procedure p11()
begin
  declare total int default 0;
  declare num int default 0;
  r:repeat
    set total:= total + num;
  set num:=num + 1;
  until num > 100
  end repeat r;
  select total;
end$