Mysql中if-else的使用

Mysql中if-else的使用

主要是对if-else的使用。这里给出一个存储过程，可以通过测试：

drop procedure if exists update_hour_total;

delimiter //

create procedure update_hour_total(out isSucceed int)
begin
	declare currentHour int; -- 设置当前的小时
	declare yesterday date;
	declare i int default 1; -- 循环变量
	
	-- 为变量赋值
	select date_format(date_sub(current_date, interval 1 day),'%Y%m%d') into yesterday;
	select hour(current_timestamp) into currentHour; 
			
	if (currentHour != 0)
	then 
		update lawson rt_1 -- 首先将总数设置成当前的amount_paid
		set rt_1.total_amount_paid  = rt_1.amount_paid;
					
		while i <= currentHour -- 如果小于当前小时
		do
			update lawson rt_1
			inner join lawson rt_2
				on rt_1.value_date = rt_2.value_date
				and rt_2.value_time = i - 1
			set rt_1.total_amount_paid = rt_1.amount_paid + rt_2.total_amount_paid
			where rt_1.value_time = i;
			
			set i = i + 1;
		end while;
	
	-- 如果当前为0时，已经把昨天23时的数据运行完毕了。这时候需要更新23时的总数
	elseif(currentHour = 0) 
	then
		update lawson rt_1 -- 首先将总数设置成当前的amount_paid
		set rt_1.total_amount_paid  = rt_1.amount_paid;
		
		set i = 23; -- 将i设置成23	
		
		update lawson rt_1
		inner join lawson rt_2
			on rt_1.value_date = rt_2.value_date							
			and rt_2.value_time = i - 1
		set rt_1.total_amount_paid = rt_1.amount_paid + rt_2.total_amount_paid
		where rt_1.value_time = i
			and rt_1.value_date = yesterday; -- 将日期设置为昨天	
	
	end if;
	
end //

delimiter ;