$a1=$_POST["txtjob_date_day"];
$a2=$_POST["txtjob_date_month"];
$a3=$_POST["txtjob_date_year"];
if(!empty($a1)){
$sql = "SELECT * FROM job WHERE job_date_day LIKE '%".$a1."%'";
}else if(empty($a1)&&!empty($a2)&& empty($a3)){
$sql = "SELECT * FROM job WHERE job_date_month LIKE '%".$a2."%'";
}else if(empty($a1)&& empty($a2) && !empty($a3)){
$sql = "SELECT * FROM job WHERE job_date_year LIKE '%".$a3."%'";
}else if(!empty($a1) && !empty($a2)){
$sql = "SELECT * FROM job WHERE job_date_day LIKE '%".$a1."%' AND job_date_month LIKE '%".$a2."%'";
}else if(!empty($a1) && !empty($a3)){
$sql = "SELECT * FROM job WHERE job_date_day LIKE '%".$a1."%' AND job_date_year LIKE '%".$a3."%'";
}else if(!empty($a2) && !empty($a3)){
$sql = "SELECT * FROM job WHERE job_date_month LIKE '%".$a2."%' AND job_date_year LIKE '%".$a3."%'";
}else if(!empty($a1) && !empty($a2) && !empty($a3) ){
$sql = "SELECT * FROM job WHERE job_date_day LIKE '%".$a1."%' AND job_date_month LIKE '%".$a2."%' AND job_date_year LIKE '%".$a3."%'";
}else{
$sql = "SELECT * FROM job";
}