当我使用concat时，Mysql查询无效

Question

I don't understand why following query is not return anything. If I change the query then it's return result.

what I'm doing now (No output)

$msg =  array();
$getSearch = "SELECT contact_details . * , company.company_name, users.nickname FROM contact_details LEFT JOIN users ON users.user_id = contact_details.user_id LEFT JOIN company ON company.cid = contact_details.cid WHERE";  

if(!empty($ad_company)){
    $getSearch .= "company.company_name LIKE '$ad_company%' ";
}     

$getSearch =  mysql_query($getSearch);  
while($searchResult =  mysql_fetch_array($getSearch)){
$msg[] = $company = $searchResult['company_name'] . "<br/>";
}
echo  json_encode($msg);        

Change Code(Working)

$msg =  array();
$getSearch = "SELECT contact_details . * , company.company_name, users.nickname FROM contact_details LEFT JOIN users ON users.user_id = contact_details.user_id LEFT JOIN company ON company.cid = contact_details.cid WHERE company.company_name LIKE '$ad_company%'"; 

//$msg[] = empty($ad_company) ? "empty company" : "not empty company"; //for checking and field has value

/*if(!empty($ad_company)){
    $getSearch .= "company.company_name LIKE '$ad_company%' ";
}*/         

$getSearch =  mysql_query($getSearch);

while($searchResult =  mysql_fetch_array($getSearch)){
$msg[] = $company = $searchResult['company_name'] . "<br/>";
}
echo  json_encode($msg);        

Answer 1

Try this

As answer by Mitja , you have missed the space between WHERE and company

$getSearch = "SELECT contact_details . * , company.company_name, users.nickname 
              FROM contact_details 
              LEFT JOIN users ON users.user_id = contact_details.user_id 
              LEFT JOIN company ON company.cid = contact_details.cid ";  

if(!empty($ad_company)){
    $getSearch .= " WHERE company.company_name LIKE '$ad_company%' ";
}  

EDITED

$getSearch = "SELECT contact_details . * , company.company_name, users.nickname 
              FROM contact_details 
              LEFT JOIN users ON users.user_id = contact_details.user_id 
              LEFT JOIN company ON company.cid = contact_details.cid
              WHERE 1=1 ";  

if(!empty($ad_company)){
    $getSearch .= " AND company.company_name LIKE '$ad_company%' ";
}