Use rank command to limit find last purchase - sql

Question

I'm trying to find the last purchase for each customer_id. Since there are 3 customers I was expecting to get back 3 rows but I'm getting more.
Can someone tell me what's wrong and how to fix this issue. Any help would be greatly appreciated
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'DD-MON-YYYY HH24:MI:SS.FF';
ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';
CREATE TABLE customers
(CUSTOMER_ID, FIRST_NAME, LAST_NAME) AS
SELECT 1, 'Faith', 'Mazzarone' FROM DUAL UNION ALL
SELECT 2, 'Lisa', 'Saladino' FROM DUAL UNION ALL
SELECT 3, 'Jerry', 'Torchiano' FROM DUAL;
CREATE TABLE items
(PRODUCT_ID, PRODUCT_NAME) AS
SELECT 100, 'Black Shoes' FROM DUAL UNION ALL
SELECT 101, 'Brown Shoes' FROM DUAL UNION ALL
SELECT 102, 'White Shoes' FROM DUAL;
CREATE TABLE purchases
(CUSTOMER_ID, PRODUCT_ID, QUANTITY, PURCHASE_DATE) AS
SELECT 1, 100, 1, TIMESTAMP'2022-10-11 09:54:48' FROM DUAL UNION ALL
SELECT 1, 100, 1, TIMESTAMP '2022-10-11 19:04:18' FROM DUAL UNION ALL
SELECT 2, 101,1, TIMESTAMP '2022-10-11 09:54:48' FROM DUAL UNION ALL
SELECT 2,101,1, TIMESTAMP '2022-10-17 19:04:18' FROM DUAL UNION ALL
SELECT 3, 101,1, TIMESTAMP '2022-10-11 09:54:48' FROM DUAL UNION ALL
SELECT 3,102,1, TIMESTAMP '2022-10-17 19:04:18' FROM DUAL UNION ALL
SELECT 3,102, 4,TIMESTAMP '2022-10-10 17:00:00' + NUMTODSINTERVAL ( LEVEL * 2, 'DAY') FROM dual
CONNECT BY LEVEL <= 5;
with cte as
(select
CUSTOMER_ID,
PRODUCT_ID,
QUANTITY,
PURCHASE_DATE,
rank() over (partition by customer_id order by purchase_date desc) rnk
from purchases
)
SELECT p.customer_id,
c.first_name,
c.last_name,
p.product_id,
i.product_name,
p.quantity,
p.purchase_date
from cte p
JOIN customers c ON c.customer_id = p.customer_id
JOIN items i ON i.product_id = p.product_id
where rnk = 1:

Answer 1

First, don't use RANK or DENSE_RANK - they will assign identical purchase_date values with the same rank and hence give you more than one "1" value. Use ROW_NUMBER instead.
Second, you have "from cte p" in there twice. Remove the second one.
And lastly, the real answer to your question is that you have a semicolon before the "where rank = 1" and so nothing after the semicolon is being executed. Hence it isn't filtering. A semicolon ends the SQL, completely.