MySql数值型字符串比较大小的坑

1.我们在做字符串数值比较大小的时候，通常会认为10比9大，但事实10却是最小的，怎么去解决这个问题，给出这样一个方案

2.现象

SELECT
	id,
	type_name AS typeName,
	type_code AS typeCode,
	pcode,
	tag_pic AS tagPic,
	is_del AS isDel 
FROM
	o2o_merchant_type 
ORDER BY
	type_code DESC;

select MAX(t1.type_code) as type_code from o2o_merchant_type as t1;
	

 我们发现字符串的10要比其他数值要小

我们发现求最大值却也是9而不是10

3.解决方法，在排序字段+0

SELECT
	id,
	type_name AS typeName,
	type_code AS typeCode,
	pcode,
	tag_pic AS tagPic,
	is_del AS isDel 
FROM
	o2o_merchant_type 
ORDER BY
	type_code + 0 DESC 

select MAX(t1.type_code + 0) as type_code from o2o_merchant_type as t1;

问题解决

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