mysql设计的时候遇到一个多选项问题，搜索了一番似乎使用SET类型比较方便实现。
虽然弄明白了SET字段的存储及查询方法，但无奈能搜到的资料有限，还是有两个问题找不到头绪。
假设字段名为 flag ，SET的预设值有 A，B，C，D，E，F，G六个。
因为SET的预设值可能会增多，那么怎么能自动读出 SET的所有的预设值呢？
对于查询含有某个或者某几个值的时候可以使用：
SELECT * FROM table WHERE FIND_IN_SET('A',flay);
SELECT * FROM table WHERE FIND_IN_SET('A,C',flay); 类似的进行查询。
但如果想要查询哪些包含一个选项（只有A或者B或者C……），哪些包含多个选项该怎么查询呢（AC，BCD什么的）？
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
This is really disgusting. There are two methods, but neither of them are very good
desc table_name set_column_nameGo to
information_schemaand selectBoth methods have poor programmability. If I were to do it, I would probably create another table to hold the list of options
There seems to be no good solution. You can use
select char_length(set_column_name) from table_name;to see the number of characters and do it indirectlyStoring in this structure will be more flexible.