SELECT

    P.CPF_CNPJ AS CpfCnpj,

    COUNT(*) AS Repeticao

FROM PESSOA P

INNER JOIN CLIENTE C ON C.ID_CLIENTE = P.ID_PESSOA

WHERE P.CPF_CNPJ IS NOT NULL AND P.CPF_CNPJ <> ''

GROUP BY P.CPF_CNPJ

HAVING COUNT(*) > 1