Oracle SQL: SUM of 'amount_sold' rows for each client - sql

Question

I need to display for each client the total /sum/ amount (from amount_sold) saved as a total_amount field. And in WHERE to set that total_amount is greater than or equal to cust_credit_limit :
total_amount >= cust_credit_limit
//
SELECT CONCAT (CONCAT(cust_first_name,' '),cust_last_name) AS customer_name,
amount_sold,
(CASE WHEN cust_credit_limit<=1500 THEN 'Low limit'
ELSE 'High limit'
END) AS credit_limit_level,
cust_valid
FROM sh.customers JOIN sh.sales
ON customers.cust_id = sales.cust_id
ORDER BY customer_name ASC;
The results now look like this:
But I need only one row for each client with the sum of all amount_sold for this client AS total_amount
**EDIT: I tried as recommended in comments and it worked. But I have another condition - to order the results by 'upper_income_level' and when I add
'lpad( substr(cust_income_level, instr( cust_income_level, '-') + 2 ), 9, '0') AS upper_income_level,'
it appears "not a GROUP BY expression".
'SELECT CONCAT (CONCAT(cust_first_name,' '),cust_last_name) AS customer_name,
lpad( substr(cust_income_level, instr( cust_income_level, '-') + 2 ), 9, '0') AS upper_income_level,
SUM(amount_sold) as total_sold,
(CASE WHEN cust_credit_limit<=1500 THEN 'Low limit'
ELSE 'High limit'
END) AS credit_limit_level,
cust_valid
FROM sh.customers JOIN sh.sales
ON customers.cust_id = sales.cust_id
WHERE cust_valid = 'A' AND cust_income_level LIKE '%-%'
GROUP BY
CONCAT (CONCAT(cust_first_name,' '),cust_last_name),
cust_valid,
cust_credit_limit
HAVING SUM(amount_sold) >= 50*cust_credit_limit
ORDER BY upper_income_level DESC, customer_name ASC;'

Answer 1

Your query shall deal with customers and their total sale. So, select from the customers table and join the aggregated total sale:
select
c.cust_first_name || ' ' || c.cust_last_name as customer_name,
to_number
(
regexp_substr(c.cust_income_level , '[0123456789,]+$'),
'999999999D999',
'nls_numeric_characters = '',.'''
) as upper_income_level,
s.total_sale,
case when c.cust_credit_limit <= 1500
then 'Low limit'
else 'High limit'
end as credit_limit_level,
c.cust_valid
from sh.customers c
join
(
select cust_id, sum(amount_sold) as total_sale
from sh.sales
group by cust_id
) s on s.cust_id = c.cust_id
and s.total_sale >= c.cust_credit_limit
where c.cust_valid = 'A'
and c.cust_income_level like '%-%'
order by upper_income_level desc, customer_name;

Answer 2

Add a SUM and a GROUP BY:
SELECT CONCAT (CONCAT(cust_first_name,' '),cust_last_name) AS customer_name,
SUM(amount_sold) as total_sold,
(CASE WHEN cust_credit_limit<=1500 THEN 'Low limit'
ELSE 'High limit'
END) AS credit_limit_level,
cust_valid
FROM sh.customers JOIN sh.sales
ON customers.cust_id = sales.cust_id
GROUP BY
CONCAT (CONCAT(cust_first_name,' '),cust_last_name),
cust_valid,
cust_credit_limit
HAVING SUM(amount_sold) >= cust_credit_limit
ORDER BY customer_name ASC;
Tips:
You might find that your concat accepts multiple parameters and concats all of them e.g. CONCAT(first_name, ' ', last_name)
Rules of GROUP BY: Anything not contained in a SUM, AVG, or similar aggregation function in your SELECT, must be in the GROUP BY. At the time GROUP BY is done, the aliases in the select list don't exist, so you must instead use the expression that prepares the result (or some child part of it such that the whole expression can be computed from grouped values)
HAVING is like a where clause that is done after a group by. WHERE is done before a group by. HAVING can hence reference grouped and aggregated expressions, but they must be grouped or aggregated

Answer 3

Try to use sum(), group by and having:
SELECT CONCAT (CONCAT(cust_first_name,' '),cust_last_name) AS customer_name,
sum(amount_sold) as total_amount,
(CASE WHEN cust_credit_limit<=1500 THEN 'Low limit'
ELSE 'High limit'
END) AS credit_limit_level,
cust_valid
FROM sh.customers JOIN sh.sales
ON customers.cust_id = sales.cust_id
GROUP BY customer_name, credit_limit_level, cust_valid
HAVING sum(amount_sold)>=max(cust_credit_level)
ORDER BY customer_name ASC;

Answer 4

if you have 2 cutomer with the same name,cust_id in group by is the must.
SELECT customers.cust_id,
CONCAT (CONCAT(cust_first_name,' '),cust_last_name) AS customer_name,
sum(isnull(amount_sold,0)) amount_sold
FROM sh.customers JOIN sh.sales
ON customers.cust_id = sales.cust_id
group by customers.cust_id,CONCAT (CONCAT(cust_first_name,' '),cust_last_name)
having sum(isnull(amount_sold,0)) >= max(cust_credit_limit)
ORDER BY customer_name ASC;