SELECT t.customer_id,
    t.create_date,
    t.loan_id,
    row_number() OVER (PARTITION BY t.customer_id ORDER BY t.create_date) AS loan_count
   FROM ( SELECT DISTINCT ON (statistic.loan_id) statistic.loan_id,
            statistic.customer_id,
            statistic.create_date
           FROM loans.statistic
          ORDER BY statistic.loan_id, statistic.statistic_date) t
  GROUP BY t.customer_id, t.loan_id, t.create_date;