PostgreSQLカウントの最大値を計算する方法

Question

最大カウント（r.customer_id）を計算する方法を見つけようとしています。スクリプトを実行すると、同じ最高値を持つ4つの値がありますので、私は生成する必要があることは、これらの4つの値

SELECT  c1.customer_id, c1.first_name, c1.last_name, count(r.customer_id) 
FROM  customer c1 
INNER JOIN rental r 
ON   (c1.customer_id = r.customer_id) 
WHERE  r.staff_id = 2 
GROUP  BY c1.customer_id, c1.first_name, c1.last_name 
ORDER BY 4 desc 

Answer 1

SELECT customer_id, first_name, last_name, count 
     FROM (
     SELECT c1.customer_id as customer_id, c1.first_name as first_name, c1.last_name as last_name, count(r.customer_id) as count 
     FROM customer c1 
     INNER JOIN rental r ON (c1.customer_id = r.customer_id ) 
     WHERE r.staff_id = 2 
     GROUP BY c1.customer_id, c1.first_name, c1.last_name 
    ) x 
    GROUP BY customer_id, first_name, last_name 
    HAVING count = max(count) 
    order by 4 desc