array(0) {
}
 all is good!<br />
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<hr>SELECT * FROM device, os, make, devicetype
             WHERE device.manufacturer_id = make.manufacturer_id
AND device.system_id = os.system_id
AND device.type_id = devicetype.type_id
 AND manufacturer_id = '' AND system_id = '' AND type_id = ''<hr><hr> <br> Your SQL:<br> SELECT * FROM device, os, make, devicetype
             WHERE device.manufacturer_id = make.manufacturer_id
AND device.system_id = os.system_id
AND device.type_id = devicetype.type_id
 AND manufacturer_id = '' AND system_id = '' AND type_id = ''<br><br>SQL Error: Column 'manufacturer_id' in where clause is ambiguous<hr>