mysql how to select from one table if the second table has no matching information

Question

I am trying to only show results from table inventoryfolders if the id does not exist in table newlisting.

Here is my query:

$sql = "SELECT * 
          FROM avirobust.inventoryfolders  
         WHERE parentFolderID = '".$foname."' 
           AND agentID = '".$mne."' 
           AND parentFolderID NOT IN (SELECT folderID FROM marketplace.newlisting)";

However it never returns a result even if newlisting has no data in it.

I know that join can work but can I use something like in my query above? If so what did I do wrong in my query?

Answer 1

You can try use this code

SELECT inventoryfolders.* FROM avirobust.inventoryfolders LEFT JOIN marketplace.newlisting on (inventoryfolders.parentFolderID = newlisting.folderID) WHERE parentFolderID = '".$foname."' AND agentID = '".$mne."' AND newlisting.folderID is NULL

It will return all records from inventoryfolders where no corresponding rows in newlisting