mysql - MySQL delete all rows with abandoned IDs

Question

In my database I have three tables: one contains words (word_id, word), the other lists categories (cat_id, cat_name) and third one assigns categories to all words (word_id, cat_id) (one or more categories per word).

Is it possible to delete all rows in the categories-to-words-table with a word_id that does not currently exist in the words table?

Answer 1

是的，通过使用这个：

DELETE FROM categories_to_words
WHERE word_id NOT IN (SELECT word_id FROM words);

有更有效的方法可以做到这一点，但这会奏效。

但是：您应该真正使用外键进行调查，因为如果您使用它们，您将不会遇到您现在正在解决的问题。

Answer 2

最直接的方法是翻译你的句子：

delete from categories2words
    where word_id not in (select word_id from words);

Answer 3

尝试这个：-

Delete from categories2words
where word_id not in (select word_id from words);