php sqlite3Result

How would the following fail:

$stmt = $db->prepare("INSERT INTO someta开发者_Go百科ble VALUES ('SOMETHING')");
$result = $stmt->execute();

What would be a scenerio when: !$result == true?

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1. Database file is not opened or not writable.
2. sometable does not exist.
3. A conflict occurs.

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1. If 'sometable' has more than 1 not-null column with no defaults. see http://www.sqlite.org/lang_insert.html first bullet, second sentence