为Mysql触发器中的变量选择值

Ok I've seen many similar questions but crawling over the answers couldn't make my trigger error free!
Result I need is: Whenever a new value is inserted in the database table temp_pool, it triggers and if the new address is not equal to the previous address value with the same dev_id as that of this NEW.dev_id insert the new values to location table.

好的，我已经看过很多类似的问题，但爬过答案无法使我的触发器无错误！我需要的结果是：每当在数据库表temp_pool中插入新值时，它就会触发，如果新地址不等于先前的地址值，并且与此NEW.dev_id具有相同的dev_id，则将新值插入位置表。

Here is the query (sample):

这是查询（示例）：

CREATE TRIGGER filter 
after insert on geo.temp_pool
for each row
BEGIN
DECLARE OLD_ADDR VARCHAR(2048);
OLD_AADR = select address from temp_pool where dev_id like NEW.dev_id
order by date desc, time desc limit 1;
IF (OLD_ADDR != NEW.address) THEN
INSERT INTO a3380361_geo.location
VALUES (NEW.dev_id,NEW.address,NEW.lat,NEW.lng,NEW.date,NEW.time);
END IF;
END
$$

I am using the phpMyAdmin editor and set the delimiter to $$.

我正在使用phpMyAdmin编辑器并将分隔符设置为$$。

The error that I am getting is:

我得到的错误是：

1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '= select address from temp_pool where 1 order by date desc, time desc limit 1; ' at line 5

I strongly believe that there is some problem with assigning values from SELECT to a variable [OLD_ADDR], so is there any way to solve my issue?
The logic is simple and the requirement is understandable from the query, right?

我坚信将SELECT中的值分配给变量[OLD_ADDR]存在一些问题，那么有什么方法可以解决我的问题吗？逻辑很简单，查询中的要求是可以理解的，对吧？

Open to all opinions and suggestions.

对所有意见和建议持开放态度。

2 个解决方案

#1

Instead of:

代替：

 OLD_AADR = select address from temp_pool where dev_id like NEW.dev_id

Use:

使用：

SET OLD_AADR = (select address 
                from temp_pool 
                where dev_id like NEW.dev_id 
                order by address 
                limit 1);

Or using the non-standard SELECT assignment statement(not sure whether mysql supports it or not):

或者使用非标准的SELECT赋值语句（不确定mysql是否支持）：

SELECT OLD_AADR = address from temp_pool where dev_id like NEW.dev_id
                  order by address 
                  limit 1;

Not that in both cases the SELECT statement has to return only a scalar value. Thats why I used LIMIT 1.

并非在两种情况下，SELECT语句都必须仅返回标量值。这就是我使用LIMIT 1的原因。

#2

Did you notice the typo?

你注意到了错字吗？

OLD_ADDR OLD_AADR

#1