In my database, I have a few fields that are strings and I am trying to write a query
that converts the string to a date based on a From and To date selected by user and only display records that were created within that date range
(as well as other options).

It was working before I added in the last 2 lines with the dates in it.

Example Code:
$sql = "SELECT p.hdr_ID , u.ID, u.display_name, p.hdr_acord_date, p.hdr_company_addr, p.hdr_app_status ";
$sql .= "FROM wp_users u ";
$sql .= "INNER JOIN wp_usermeta m ON m.user_id = u.ID ";
$sql .= "INNER JOIN wp_policies p ON p.hdr_sales_num = u.ID ";
$sql .= "WHERE m.meta_key = 'wp_capabilities' AND m.meta_value LIKE '%salesperson%' ";
$sql .= "AND p.hdr_sales_num = $sSalesID ";
$sql .= "AND p.hdr_app_status = '$sAppStatus' ";

$sql .= "AND STR_TO_DATE($sAccordFromDate, '%m/%d/%Y') >= STR_TO_DATE(p.hdr_acord_date, '%m/%d/%Y') ";
$sql .= "AND STR_TO_DATE($sAccordToDate, '%m/%d/%Y') <= STR_TO_DATE(p.hdr_acord_date, '%m/%d/%Y') ";

Any help is much appreciated.