I need the second option, because the field2 can be also empty. Inserting the string:

( ( `cb_field1` LIKE '%[cb_field2]%' ) OR ( '[cb_field2]' = '' ) )

if the field2 is populated and finds correspondence with the field1, gives me the correct users, if it does not find the correspondence returns nothing. The problem occurs when the field2 is empty because it returns all the data, seems that the part " OR ( '[cb_field2]' = '' ) " is not performed.

I apologize, but I meant to say different and not equal "OR ( '[cb_field2]' <> '' ) )" and not "OR ( '[cb_field2]' = '' ) )".
However, I solved by replacing the LIKE operator with "="

(( `cb_field1` = '[cb_field2]' ) OR ('[cb_field2]' != '')

so data entry is constrained by fixed values ​​contained in the dropdown. Now, however, I would check also that the field1 is different from empty and I set the string:

(( `cb_field1` = '[cb_field2]' ) OR ('[cb_field2]' != '') OR (`cb_field1` != ''))

but it does not work, it is possible to do so?.
Thank you.

I solved this way:

( ( ( `cb_field1` = '[cb_field2]' ) OR ( '[cb_field1]' != '' ) ) AND ( '[cb_field2]' != '' ) )

I have done several tests and it seems to work well, I hope it is a valid method.
Thank you.

Hi, I installed CB 2.0, everything works fine except the userlist. I saw that I must to add the prefix "eu." for the columns of the tables cb_comprofiler so I changed my string:

( ( ( ue.`cb_field1` = '[cb_field2]' ) OR ( '[cb_field1]' != '' ) ) AND ( '[cb_field2]' != '' ) )

but the filter does not work and I get the message:

"There are no published user lists!"