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Formatted question description: https://leetcode.ca/all/2205.html

# 2205. The Number of Users That Are Eligible for Discount

## Description

Table: Purchases

+-------------+----------+
| Column Name | Type     |
+-------------+----------+
| user_id     | int      |
| time_stamp  | datetime |
| amount      | int      |
+-------------+----------+
(user_id, time_stamp) is the primary key 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 an SQL query to report the number of users that are eligible for a discount.

The query result format is in the following example.

Example 1:

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.


## Solutions

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