mysql觸發器問題

Question

看了資料庫的觸發器，就想，如果某個定單表插入的數量大於商品表，那麼商品表應該是負數啊，應該加以限制。可是我採用before來限制時，則不能執行，誰幫我看下這串程式碼哪錯了

create trigger tg1

before insert on ord

for each row

begin

##if new.o_num > goods.g_num then

set new.o_num = goods.g_num

end if;

update goods set g_num = g_num - new.o_num where gid = new.gid;

end$

Answer 1

if new.o_num > goods.g_num then

set new.o_num = goods.g_num

當DD的數量大於庫存數量你讓DD的數量等於庫存的數量了你可以用phpmyadmin來建造觸發器

Answer 2

你這個也不需要 觸發器來做 買之前 限制買的數量