DEDECMS Two-time development multi-category selection

DEDECMS Two-time development of various types of selection
When you modify DEDECMS, you can select multiple places of use when you want to add a product to your application. That is, you can select multiple uses.
How can I change the database? How to save the results of multi-column selection, how to pass the value of the good?
The gods take care of you.


------Solution--------------------
According to the database paradigm, 1:n needs a separate table, a row for a selection relationship, a user to select multiple, then multiple lines, at least for (user + selection) to establish a unique index (also can be done as primary key), as needed can increase the self-increment as primary key.

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