Problem

Table: Purchases

1
2
3
4
5
6
7
8
9

+-------------+----------+
| Column Name | Type     |
+-------------+----------+
| user_id     | int      |
| time_stamp  | datetime |
| amount      | int      |
+-------------+----------+
(user_id, time_stamp) is the primary key (combination of columns with unique values) for this table.
Each row contains information about the purchase time and the amount paid for the user with ID user_id.

A user is eligible for a discount if they had a purchase in the inclusive interval of time [startDate, endDate] with at least minAmount amount. To convert the dates to times, both dates should be considered as the start of the day (i.e., endDate = 2022-03-05 should be considered as the time 2022-03-05 00:00:00).

Write a solution to report the number of users that are eligible for a discount.

The result format is in the following example.

Examples

Example 1

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22

Input: 
Purchases table:
+---------+---------------------+--------+
| user_id | time_stamp          | amount |
+---------+---------------------+--------+
| 1       | 2022-04-20 09:03:00 | 4416   |
| 2       | 2022-03-19 19:24:02 | 678    |
| 3       | 2022-03-18 12:03:09 | 4523   |
| 3       | 2022-03-30 09:43:42 | 626    |
+---------+---------------------+--------+
startDate = 2022-03-08, endDate = 2022-03-20, minAmount = 1000
Output: 
+----------+
| user_cnt |
+----------+
| 1        |
+----------+
Explanation:
Out of the three users, only User 3 is eligible for a discount.
 - User 1 had one purchase with at least minAmount amount, but not within the time interval.
 - User 2 had one purchase within the time interval, but with less than minAmount amount.
 - User 3 is the only user who had a purchase that satisfies both conditions.

Solution

Method 1

Code

 1
 2
 3
 4
 5
 6
 7
 8
 9
10

CREATE FUNCTION getUserIDs(startDate DATE, endDate DATE, minAmount INT) RETURNS INT
BEGIN
  RETURN (
      # Write your MySQL query statement below.
      SELECT COUNT(DISTINCT user_id)
      FROM Purchases
      WHERE (time_stamp BETWEEN startDate AND endDate) AND
            amount >= minAmount
  );
END