Is there a way that people can only add a certain field only one time per ID field

[nanglin]

Example

I have a dropdown that lists book 1, book 2, book 3 etc...

The store ID can only add the books one time. So store 1 can have book 1 with all book 1's information and book 2 with all book 2's information etc... but they cannot have book 1, book1, and book 2. Store 2 can also have book 1 with all book 1's information. So being unique in the table does not work since it can be used multiple times. 

Is there any solution for this. Currently us the user can add any of the options. 

[TellMeWhy]

Hi @nanglin,

If I understand it correctly, you have a table of 'records' where each row displays an entry of what book is added into what store?

e.g.

Records Table

| ID  |    Store    | Book
|        |                    |
|ID1 | Store 2 | Book 2 ...
|ID2 | Store 1 | Book 3 ...
|ID3 | Store 2 | Book 3 ...

If this is the case, we can use the method that is mentioned here 

-create a formula field in the records table
-concatenate the Store ID with the Book ID (convert both into text if they're in number format as to avoid arithmetic addition instead of concatenation) 
-make the Formula field in the table unique. In that way, if another entry is submitted to the 'records' table with the same concatenated value, the submission form will display an error instead of inputting the data into the table.
*You can change the error message in the Localization Tab of the Caspio Bridge and using it on the specific datapage

Hope this is the solution you're looking for. Good Luck!