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POStoring Secondary Data Based on Primary Selection
 

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    <p>Generically, I'm wondering how I would store secondary data based on the type of primary data.</p> <p>Here's the real-world situation. When adding "students" to my database, I want to start their referral. This will be done by referencing a table called "referrer" that stores a list of options that will appear in a drop-down box, as such:</p> <pre><code>+-------------+---------------+ | referrer_id | referrer | +-------------+---------------+ | 1 | Student | | 2 | Search Engine | | 3 | Ad | +-------------+---------------+ </code></pre> <p>So in the student's table, I'll store the referrer_id -- Easy enough.</p> <p>Based on the selection, I'd like the user to be able to enter secondary information. For instance, if they choose "Student" from the list, a second drop-down box will appear presenting them with a list of existing students so they can specify which student was the referrer, and I would want to store the student_id. If they chose either "Search Engine", I would present them with a text box where they can enter the name of the search engine, and I would store that text.</p> <p>So my question is, how should me "students" table be structured in order to hold this information, since sometimes I'll be storing a student_id, or the text entered in a box, or... ? My initial thought is to create additional columns in the students table to hold the various possibilities, but that seems both messy and not scalable, so I don't care for it. I'm wondering if an additional cross-reference table would be warranted here, that would hold the student_id, the referrer_id, and then a value (such as the referring student_id, or the value entered into the text box). Or perhaps instead of "value", I could have "value_id", "value_text", and so on for different data type possibilities. The value of referrer_id in this table would tell me which column contains the data I want. While this seems cleaner than expanding out the students table, it does still seem a bit messy.</p>
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