列表不在内部联接中的ID

I have a SELECT statement that provides me with a list of relevant IDs and company names that match the criteria. Here is the statement:

$result = mysqli_query($con,"SELECT a.OWNER_ID,b.ID, b.TITLE AS companyname FROM b_crm_act a INNER JOIN b_crm_company b ON a.OWNER_ID = b.ID");

while($row = mysqli_fetch_array($result))
{
echo "<tr>";
echo "<td>" . $row['ID'] . "</td>";
echo "<td>" . $row['companyname'] . "</td>";
echo "</tr>";
}
echo "</table>";

This lists all the IDs and company names. What I actually need is a list of IDs from b_crm_company that aren't in b_crm_act. I'm thinking I use NOT IN function but I've tried this and it's not listing anything.

Your help would be appreciated.

you can use LEFT JOIN on this

SELECT  a.ID, 
        a.TITLE AS companyname 
FROM    b_crm_company a 
        LEFT JOIN b_crm_act b 
            ON a.ID = b.OWNER_ID // <== specify how the tables are linked
WHERE   b.OWNER_ID IS NULL       // <== a value of NULL when it doesn't exists

Not sure about your column names but this is how it looks like.

I don't know how efficient this is but have you tried using a NOT IN subquery?

SELECT ID,title FROM b_crm_company WHERE ID NOT IN( SELECT ID FROM b_crm_company INNER JOIN b_crm_act ON b_crm_act.OWNER_ID = b_crm_company.ID )