doesn't support upsert-ish behaviour

the following query fails in test, but passes in mysql.

```
INSERT INTO `user_lauer_testing`
SET `user_id` = '123',
`username` = 'mike'
ON duplicate KEY
UPDATE `user_id` = '123',
`username` = 'bob'
```

Begin by reproducing the SQL query shown in issue #11 through the failing test, then trace how nquery parses INSERT with ON DUPLICATE KEY UPDATE. Compare the result with MySQL; done means this query no longer fails and its upsert behavior is compatible with the stated MySQL result.

Written by the indexing model from the issue text.