计算重复信息对的数量

Question

I have a table with customer_ID, date, and payment_method as 3 columns. payment_method can be 'cash', 'credit', or 'others'. I want to find out the number of customers who have used credit as a payment method more than 5 times, in the last 6 months.

I found this solution for displaying the rows where the customer used credit:

SELECT customer_ID, payment_method, COUNT(*) AS unique_pair_repeats
FROM tab1
WHERE customer_ID IS NOT NULL
GROUP BY customer_ID, payment_method
HAVING count(*) > 1;

The problem is, I don't want a list of the names/ids, I want to know how many people used their credit card for a purchase 5 times or more in the last 6 months.

Answer 1

This is one way you could do it:

SELECT COUNT(*) 
FROM 
(
  SELECT customer_id 
  FROM tab1
  WHERE 
    customer_ID IS NOT NULL and 
    payment_method = 'credit' and 
    tran_date > add_months(sysdate, -6)
  GROUP BY customer_ID
  HAVING count(*) > 5
) x

The inner query generates a list of all customer ids that have used credit more than 5 times in 6 months. The outer query counts them

You might feel it more logical to write it like this:

SELECT COUNT(*) 
FROM 
(
  SELECT customer_id, count(*) as ctr 
  FROM tab1
  WHERE 
    customer_ID IS NOT NULL and 
    payment_method = 'credit' and 
    tran_date > add_months(sysdate, -6)
  GROUP BY customer_ID
) x
WHERE x.ctr > 5

Answer 2

So, remove customer_ID, payment_method, from select .

Though, that still doesn't answer "at least 5 times in last 6 months", so you need another condition: date (presuming you use Oracle, although you didn't tag the question but - you do use Oracle SQL Developer):

and date_column >= add_months(trunc(sysdate), -6)

Finally, something like this might help:

SELECT COUNT(*) AS unique_pair_repeats                 --> changes here
FROM tab1
WHERE customer_ID IS NOT NULL
  and date_column >= add_months(trunc(sysdate), -6)    --> here
GROUP BY customer_ID, payment_method
HAVING count(*) >= 5;                                  --> here