Counting Values on Custom Page

I suspect that you have defined the fields “INVOICE_NO” and/or “SUPPLIER” as Persistent Custom fields of type “Reference”? If so you have to check the _DB column instead:

• WHERE cf$_supplier_db = :cf$_supplier AND cf$_invoice_no_db = :cf$_invoice_no

The reason is the following:

• For Persistent Custom Fields of type “Reference” the table (_CFT, _CLT) stores the ROWKEY of the referenced record rather than the actual key you are referencing. The ROWKEY is a GUID, i.e. a ‘random’ string of characters and numbers.
• In the corresponding view (_CFV, _CLV) you then get two columns, a _DB column (e. g. “CF$_SUPPLIER_DB”) which shows the ROWKEY value from the table and the standard column (“CF$_SUPPLIER”) which shows the now converted user friendly value (i.e. the supplier id).
• As the parameters (:CF$_SUPPLIER / t.CF$_SUPPLIER) come from the table these will contain the ROWKEY
• Your select statement has its WHERE condition on the view though where it then contains the converted (user friendly) key value. 
• To fix this you can either change your select statement to select from the table (“i_n_v_r_e_g_clt”) or select form the _db column.

Hope this helps!