php - SQL OR functioning like AND -

this relevant line of code:

$woquery = $dbc->prepare("select * workorder statusid <> 15 or statusid <> 12 order datein asc");

the problem having code, or function seems working , function.

if change (for example):

statusid <> 15 or statusid <> 15

then correctly excludes records 15 statusid, same if set 12

if have single function no or, filters correctly. however, when have both, filters neither 12 or 15.

use not in 2 or operations

$woquery = $dbc->prepare("select * workorder statusid not in( 15, 12) order datein asc"

M16