Hey everyone! I'm running into an "OperationalError: foreign key mismatch" while trying to work through the "Joining Multiple Tables with Foreign Keys" section in Chapter 16 of my SQLite tutorial. You can check out my database setup here: [link](https://pastebin.com/2qM8CaAA). From what I've gathered, it seems the issue might be that my 'cats' table doesn't have a defined primary key. I read that SQLite automatically creates a rowid but that can't be used as a reference for foreign keys. I'm confused about whether this is a universal issue or only with non-STRICT tables.
Can someone help confirm or clarify this for me? If I need to declare a primary key, what's the best way to do that without losing my existing data? Is it as straightforward as renaming the current table, creating a new one with a primary key, copying the data over, and then dropping the old table? Appreciate any help! Thanks!
2 Answers
Yeah, you definitely need to define a primary key in the cats table if you're going to reference it from other tables. Rowid can't be used as a foreign key target. As DevGuruX mentioned, the process typically involves renaming your original table, creating a new one, and transferring the data. If you've got a lot of data, be sure to back it up first. And don't get too discouraged about these hiccups—it's pretty common to run into this in SQL especially as you're starting out!
It looks like the issue might actually be tied to how you're trying to define your foreign key. You might be working with a mismatched reference if you’re trying to reference 'rowid'. In SQLite, while 'rowid' exists, it should mostly be used just for internal purposes. Instead, try explicitly defining a primary key in your 'cats' table for foreign key references.
It's also crucial to ensure that your creation statements are correct. Watch out for syntax errors like the one you hit earlier with unterminated strings. If your current table lacks a proper primary key, you'll have to rename it, create a new one with the correct key setup, copy the data over, and drop the old table.
But don’t worry, this approach won’t lead to data loss. Just make sure you handle the copying process carefully! Good luck!
Thanks for the insight! So, just to confirm, once I create a new 'cats' table with a defined primary key, I can just use INSERT INTO...SELECT to move the data over to avoid any data loss, right?
I appreciate the encouragement! I thought I was missing something major, but it seems pretty standard. I'll proceed with the renaming and new key setup. Thanks a lot!