How to filter null values in Zoho CRM REST API?

How to filter null values in Zoho CRM REST API?

Hi there,

Lets say if I want to filter some column with empty value.

If the column is a normal column, I mean not a predefined column. Then this works:

https://crm.zoho.com/crm/private/xml/Accounts/searchRecords?scope=crmapi&newFormat=2&authtoken=myaccesstoken&criteria=(Billing Code:"")

But if it's a predefined column, then we need to use getSearchRecordsByPDC function, right?

But this doesn't work:

https://crm.zoho.com/crm/private/xml/Contacts/getSearchRecordsByPDC?scope=crmapi&authtoken= myaccesstoken&searchColumn=email&searchValue=""

How do we filter the null values then?

Thanks.