oracle数据库支持物化视图--不是基于基表的虚表，而是根据表实际存在的实表，即物化视图的数据存储在非易失的存储设备上。 下面实验创建ON COMMIT 的FAST刷新模式，在mysql中用触发器实
oracle数据库支持物化视图--不是基于基表的虚表，而是根据表实际存在的实表，即物化视图的数据存储在非易失的存储设备上。 下面实验创建ON COMMIT 的FAST刷新模式，在mysql中用触发器实现insert , update , delete 刷新操作 1、基础表创建，Orders 表为基表，Order_mv为物化视图表 复制代码 代码如下: mysql> create table Orders( -> order_id int not null auto_increment, -> product_name varchar(30)not null, -> price decimal(10,0) not null , -> amount smallint not null , -> primary key (order_id)); Query OK, 0 rows affected mysql> create table Order_mv( -> product_name varchar(30) not null, -> price_sum decimal(8.2) not null, -> amount_sum int not null, -> price_avg float not null, -> order_cnt int not null, -> unique index(product_name)); Query OK, 0 rows affected 2、insert触发器 复制代码 代码如下: delimiter $$ create trigger tgr_Orders_insert after insert on Orders for each row begin set @old_price_sum=0; set @old_amount_sum=0; set @old_price_avg=0; set @old_orders_cnt=0; select ifnull(price_sum,0),ifnull(amount_sum,0),ifnull(price_avg,0),ifnull(order_cnt,0) from Order_mv where product_name=new.product_name into @old_price_sum,@old_amount_sum,@old_price_avg,@old_orders_cnt; set @new_price_sum=@old_price_sum+new.price; set @new_amount_sum=@old_amount_sum+new.amount; set @new_orders_cnt=@old_orders_cnt+1; set @new_price_avg=@new_price_sum/@new_orders_cnt; replace into Order_mv values(new.product_name,@new_price_sum,@new_amount_sum,@new_price_avg,@new_orders_cnt); end; $$ delimiter ; 3、update触发器 复制代码 代码如下: delimiter $$ create trigger tgr_Orders_update before update on Orders for each row begin set @old_price_sum=0; set @old_amount_sum=0; set @old_price_avg=0; set @old_orders_cnt=0; set @cur_price=0; set @cur_amount=0; select price,amount from Orders where order_id=new.order_id into @cur_price,@cur_amount; select ifnull(price_sum,0),ifnull(amount_sum,0),ifnull(price_avg,0),ifnull(order_cnt,0) from Order_mv where product_name=new.product_name into @old_price_sum,@old_amount_sum,@old_price_avg,@old_orders_cnt; set @new_price_sum=@old_price_sum-@cur_price+new.price; set @new_amount_sum=@old_amount_sum-@cur_amount+new.amount; set @new_orders_cnt=@old_orders_cnt; set @new_price_avg=@new_price_sum/@new_orders_cnt; replace into Order_mv values(new.product_name,@new_price_sum,@new_amount_sum,@new_price_avg,@new_orders_cnt); end; $$ delimiter ; 4、delete触发器 复制代码 代码如下: delimiter $$ create trigger tgr_Orders_delete after delete on Orders for each row begin set @old_price_sum=0; set @old_amount_sum=0; set @old_price_avg=0; set @old_orders_cnt=0; set @cur_price=0; set @cur_amount=0; select price,amount from Orders where order_id=old.order_id into @cur_price,@cur_amount; select ifnull(price_sum,0),ifnull(amount_sum,0),ifnull(price_avg,0),ifnull(order_cnt,0) from Order_mv where product_name=old.product_name into @old_price_sum,@old_amount_sum,@old_price_avg,@old_orders_cnt; set @new_price_sum=@old_price_sum - old.price; set @new_amount_sum=@old_amount_sum - old.amount; set @new_orders_cnt=@old_orders_cnt - 1; if @new_orders_cnt>0 then set @new_price_avg=@new_price_sum/@new_orders_cnt; replace into Order_mv values(old.product_name,@new_price_sum,@new_amount_sum,@new_price_avg,@new_orders_cnt); else delete from Order_mv where product_name=@old.name; end if; end; $$ delimiter ; 5、这里delete触发器有一个bug，就是在一种产品的最后一个订单被删除的时候，Order_mv表的更新不能实现，不知道这算不算是mysql的一个bug。当然，如果这个也可以直接用sql语句生成数据，而导致的直接后果就是执行效率低。 复制代码 代码如下: -> insert into Order_mv -> select product_name ,sum(price),sum(amount),avg(price),count(*) from Orders -> group by product_name;
