AND condition not working in MySQL Query

dotman14

Please i need your help with my script. Whenever i include

AND maintable.semester_name = '$semester_name'

in the MySQL Query, it returns 0 for both values of semester_name, when actually
only one is supposed to have a value of 0 when echo $nums is processed. When i
remove

AND maintable.semester_name = '$semester_name'

the query gives normal results as i expect.

Thanks.

$query = "SELECT *             
   FROM maintable 
   WHERE maintable.matric_no = '$matric_no'
   AND   maintable.session = '$session'
   AND   maintable.semester_name = '$semester_name'
   AND   maintable.level = '$level'";
$result = mysql_query($query);
$nums = mysql_numrows($result);
echo $nums ;                  

TABLE STRUCTURE

COURSES
  course_id int(100) 
  course_code varchar(100) 
  course_title varchar(100) 
  course_unit int(10) 

MAINTABLE
  maintable_id int(255) 
  matric_no int(10) 
  session varchar(10) 
  semester_name varchar(10) 
  course_code varchar(10) 
  level int(10) 
  score int(10) 
  grade varchar(4) 

RESULT_UPLOAD
  upload_id int(10) 
  session varchar(10) 
  semester_name  varchar(10) 
  course_code varchar(10) 
  level varchar(10) 

SEMESTER
  semester_id int(10) 
  semester_name varchar(10) 

STUDENT
  matric_no int(10) 
  first_name varchar(100) 
  last_name varchar(100) 
  other_name varchar(100) 
  level int(10) 

USERS
  users_id int(10) 
  title varchar(20) 
  first_name varchar(20) 
  last_name varchar(20) 
  username varchar(20) 
  password varchar(100) 
  register_date datetime 
  tmp_name varchar(100) 
  type varchar(20) 
  name varchar(20) 
  size int(10) 

YEAR
  level_id int(10) 
  level int(10)