ON DUPLICATE KEY UPDATE - add to existing value

Question

I have SQL (MySQL 5.x) query like:

           INSERT INTO table (val1),
           ON DUPLICATE KEY UPDATE `val1` = VALUES(`val1`)

And this

Answer 1

Right at the top of the fine manual you will see an example of exactly the sort of thing you're trying to do:

INSERT INTO table (a,b,c) VALUES (1,2,3)
  ON DUPLICATE KEY UPDATE c=c+1;

So you're looking for this:

connection.execute(%Q{
    INSERT INTO table (val1) VALUES(#{connection.quote(x)})
    ON DUPLICATE KEY UPDATE `val1` = `val1` + #{connection.quote(ruby_variable)}
})

Where x is what you're trying to insert and ruby_variable is what you want to add to val1 when there is a duplicate. You need a VALUES for the INSERT, not for the ON DUPLICATE.