Drupal FAPI form calls callback twice - drupal

Question

First post on stack overflow... so go easy on me!
There doesn't seem to be a suitable solution to the Drupal FAPI multiple callback issue for simple form submissions.
THE PROBLEM: My form, when submitted, adds two entries to the respective database table. Given that there is only one call to add it to the database, I feel it's safe to assume that the query is run twice (hence the dual entries).
The following code may help to provide a basis for a solution. Oh, it's Drupal 7 too, so documentation is still very much D6 centric.
function mymodule_sidebar_form_add_submit(&$form, &$form_state) {
$form_values = $form_state['values'];
$se_title = check_plain(trim($form_values['title']));
$se_link = url(trim($form_values['link']));
$se_content = check_plain(trim($form_values['content']));
$se_image = isset($form_values['image']) ? $form_values['image'] : '';
// The multi-line part below is actually a single line the real code
$query = sprintf("INSERT INTO sidebar_element(title, image_url, content)
VALUES ('%s', '%s', '%s');", $se_title, $se_image, $se_content);
db_query($query);
drupal_set_message(t('Sidebar Element has been added successfully.'));
}
... and my form function contains a submit button:
$form['submit'] = array(
'#value' => t('Add Sidebar'),
'#type' => 'submit',
'#title' => t('Add Sidebar'),
'#submit' => array('mymodule_sidebar_form_add_submit'),
);
I guess the questions I need answered are:
Why is there a double callback in the first place?
Is there a way to identify the first callback?
Thanks in advance to all.

Answer 1

$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Save')
);
$form['#submit'] = array('my_form_submit');
And replace
// The multi-line part below is actually a single line the real code
$query = sprintf("INSERT INTO sidebar_element(title, image_url, content)
VALUES ('%s', '%s', '%s');", $se_title, $se_image, $se_content);
db_query($query);
with
// The multi-line part below is actually a single line the real code
$query = "INSERT INTO {sidebar_element} (title, image_url, content)
VALUES ('%s', '%s', '%s')";
db_query($query, $se_title, $se_image, $se_content);

Answer 2

For Drupal 7
// Add the buttons.
$form['actions'] = array('#type' => 'actions');
$form['actions']['submit'] = array(
'#type' => 'submit',
'#access' => my_func(),
'#value' => t('Save'),
'#weight' => 100,
'#submit' => array('my_form_submit'),
);
As example read node_form() code

Answer 3

To find out where the second call is coming from, the easiest way is to install devel.module and use ddebug_backtrace() in your submit callback. You might need to disable the HTTP redirecto to see it, too (exit()).
But more importantly, use the API, Luke!
<?php
db_insert('sidebar_element')
->fields(array(
'title' => $se_title,
'image_url' => $se_image,
'content' => $se_content,
))
->execute():
?>
This is how your insert query should look like, what you are doing is insecure!
And for SELECT, use db_query() with named placeholders:
<?php
$result = db_query('SELECT * FROM {sidebar_element} WHERE title = :title', array(':title' => $something));
?>