假设我使用sql查询：
select * from table t where t.name = "adam" and t.age > 10;
并且在＆＃34; age＆＃34;列中，不仅仅是整数值。还有价值观＆＃34; old＆＃34;，＆＃34; young＆＃34;等...
此查询的结果将是年龄超过10岁的所有亚当，但也包含年龄等于其中一个字符串值的所有亚当＆＃34; old＆＃34;， ＆＃34;年轻＆＃34;等...
为什么会这样？
答案 0 :(得分：1)
The reason for this behavior is MySQLs Type Conversion which occurs implicit when you apply operators to data/columns of different types.
To the example you posted: It's generally considered bad practice to save data of different types/meanings in the same field.
I'd set the type of your 'age' column to 'int', and make it nullable. Then add another column named about_age which could be an ENUM with the values old and young. Whenever the 'age' column is NULL, your application can check the the about_age column. Only with this way, it's completely clear what your data means.