Question

Right now I have a table with an auto increment id number, a name, and a definition
I am updating the table with values from another table using

INSERT INTO words(id, word, definition) SELECT id, word, definition FROM temp 
ON DUPLICATE KEY UPDATE words.word = temp.word, words.definition=temp.definition;

The table temp has the same exact column layout as the table I am using, and it works fine except when I delete an entry from the middle of temp and then update my main table.
For example,

temp
id  word definition
1   bob   is a cat
2   sam   is a dog
3   doug  is a monk
4   croe  is a bird

table main is set to that
Then I remove row 2 from temp

temp
    id  word definition
    1   bob   is a cat
    2   doug  is a monk
    3   croe  is a bird

and then update main table

main
id  word definition
1   bob   is a cat
2   sam   is a dog
3   croe  is a bird
4   croe  is a bird

because temp only has 3 rows now, but main HAD 4, the 4th row isn’t deleted. I tried to fix this by making word a unique column, and now I get the error that there is a duplicate entry for key ‘word’.
So how do I fix this?

Answer 1

From the MySQL manual,

In general, you should try to avoid using an ON DUPLICATE KEY UPDATE
clause on tables with multiple unique indexes.

so, what you could do is make word your primary key, and get rid of the id column. That should do the trick 🙂

Your query then becomes

INSERT INTO words(word, definition) SELECT word, definition FROM temp 
ON DUPLICATE KEY UPDATE words.word = temp.word, words.definition=temp.definition;

If you need arbitrary sorting, I would create an additional table

CREATE TABLE word_order (VARCHAR(30) PRIMARY KEY, sort_order INT)

and then when you run your queries

SELECT words.word,
       words.definition
FROM words
JOIN word_order
ON words.word = word_order.word
ORDER BY word_order.sort_order

Your INSERTS become a little more complicated though, you’d have to run multiple inserts. See sql – insert into multiple tables in one query.

Also, this CodeProject article has some more ideas on the topic.