Query of CustomFields

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I have a custom field in Orgs, which would like to have a search only of this field with distinct, because if it is many records, the query is not running.

Any suggestion?

Here is the query:

SELECT distinct Organization.Industry.ID, Organization.Industry.LookupName FROM Organization WHERE Organization.CustomFields.c.cod_oito_principal is not null

The distinct is not working, and when it does it does not execute because it returns information that there are many records.

Thanks!