Aggregating table values by dates in table [SQL] - sql

Question

I have a table with cust_id, sku, date, order_number (if it's that customer's 1st, 2nd...) and amount. My end goal is to find the total spent by each customer during their first year (exact dates will be relative to each customer).
The sales data table is rld_sales with the following columns:
cust_id
sku,
date of purchase,
order number (if it's that customer's 1st or 2nd...)
-- CREATES TABLE OF CUSTOMER_ID AND Y1, Y2 [END DATES]
CREATE TABLE customer_timetable AS (SELECT
rld_sales. "customer_id" AS cust_id,
CAST(date(rld_sales."date") + INTERVAL '1 year' AS DATE) as y1,
CAST(date(rld_sales."date") + INTERVAL '2 year' AS DATE) as y2
FROM
rld_sales
WHERE
transaction_order = 1
GROUP BY
rld_sales. "customer_id",
date
);
-- JOINS CUSTOMER_TIMETABLE WITH RLD_SALES
CREATE TABLE t1 AS (
SELECT
customer_timetable.cust_id,
customer_timetable.y1,
customer_timetable.y2,
rld_sales.*
FROM
customer_timetable
JOIN rld_sales ON (customer_timetable.cust_id = rld_sales.customer_id)
);
SELECT
t1. "cust_id",
SUM(t1. "amount"),
SUM(t2. "amount")
FROM
t1
WHERE
CAST(date AS DATE) BETWEEN y1
AND y2
LEFT JOIN (
SELECT
t1. "amount"
FROM
t1
WHERE
CAST(date AS DATE) > t1. "y2") t2 ON t1. "cust_id" = t2. "cust_id"
GROUP BY
t1. "cust_id"
SELECT
*
FROM
customer_timetable;
So far I've had minimal success creating intermediate tables and joining one at a time, but I feel like there has to be a much more elegant way to make it all happen in a single query.

Answer 1

If I guess you are using MySQL database, This following query will give you some guideline of writing standard SQL to achieve your requirement-
SELECT
A.customer_id,
CASE
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -1 YEAR) THEN 'Last_Year'
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -2 YEAR) THEN 'Last_Previous_Year'
ELSE 'Before_That'
END 'Year',
SUM(amount) -- Not sure your amount in which table. Add Table Alias before the coulmn name if required
FROM rld_sales A
INNER JOIN customer_timetable B ON A.customer_id = B.cust_id
GROUP BY
A.customer_id,
CASE
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -1 YEAR) THEN 'Last_Year'
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -2 YEAR) THEN 'Last_Previous_Year'
ELSE 'Before_That'
END
To get yearly values per column ID wise, use this following query-
SELECT A.customer_id,
SUM(CASE WHEN A."Year" = 'Last_Year' THEN Amount ELSE 0 END) 'Last_Year',
SUM(CASE WHEN A."Year" = 'Last_Previous_Year' THEN Amount ELSE 0 END) 'Last_Previous_Year',
SUM(CASE WHEN A."Year" = 'Before_That' THEN Amount ELSE 0 END) 'Before_That'
FROM
(
SELECT
A.customer_id,
CASE
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -1 YEAR) THEN 'Last_Year'
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -2 YEAR) THEN 'Last_Previous_Year'
ELSE 'Before_That'
END 'Year',
SUM(amount) Amount -- Not sure your amount in which table. Add Table Alias before the coulmn name if required
FROM rld_sales A
INNER JOIN customer_timetable B ON A.customer_id = B.cust_id
GROUP BY
A.customer_id,
CASE
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -1 YEAR) THEN 'Last_Year'
WHEN A."date" >= DATE_ADD(CAST(NOW() AS DATE), INTERVAL -2 YEAR) THEN 'Last_Previous_Year'
ELSE 'Before_That'
END
)A
GROUP BY A.customer_id

Answer 2

I would write this as:
select s.customer_id, sum(s.amount)
from rld_sales s
where s.date < (select min(s2.date) + interval 1 year
from rld_sales s2
where s2.customer_id = s.customer_id
)
group by s.customer_id;
Temporary tables would only seem to make this query more complicated.