postgresql mathematical formula error - postgresql

Question

Hi I am trying to use a mathematical function on each row in postgresql.
But It gives me a error.
My Query:
Select
stock_inventory_line.product_code AS Sku,
COUNT(sale_order_line.name) AS Qty_Sold,
stock_inventory_line.product_qty AS Current_Qty,
(stock_inventory_line.product_qty / Qty_Sold) AS NOM
From
sale_order_line,
product_product,
product_template,
product_category,
stock_inventory_line
WHERE
sale_order_line.product_id = product_product.id AND
product_product.product_tmpl_id = product_template.id AND
product_template.categ_id = product_category.id AND
product_product.default_code = stock_inventory_line.product_code
GROUP BY
Sku,
Current_Qty,
NOM;
On this Query It gives me a error: column qty_sold doesn't exist.
If i change the 5th line to
(stock_inventory_line.product_qty / COUNT(sale_order_line.name)) AS NOM
It gives me an error: Aggregate functions not allowed in group by.

Answer 1

You are trying to use COUNT(sale_order_line.name) as a group by item. Aggreagte functions work on grouped item. They are not for grouping them.
I do not know your tables but try
Select
stock_inventory_line.product_code AS Sku,
COUNT(sale_order_line.name) AS Qty_Sold,
stock_inventory_line.product_qty AS Current_Qty,
(stock_inventory_line.product_qty / COUNT(sale_order_line.name)) AS NOM
From
sale_order_line,
product_product,
product_template,
product_category,
stock_inventory_line
WHERE
sale_order_line.product_id = product_product.id AND
product_product.product_tmpl_id = product_template.id AND
product_template.categ_id = product_category.id AND
product_product.default_code = stock_inventory_line.product_code
GROUP BY
stock_inventory_line.product_code,
stock_inventory_line.product_qty;
Basically I remove NOM from the GROUP BY. It is a product for each group, not something you group by.

Answer 2

I run into problems like this all the time. Using a CTE always works for me. Do your aggregations inside the CTE then when you call them in the outer statement, Postgres sees them as numeric instead of aggregations. Your query might run a bit faster too!
Example:
WITH cte AS(
SELECT
sale_order_line.product_id,
stock_inventory_line.product_code,
stock_inventory_line.product_code AS Sku,
COUNT(sale_order_line.name) AS Qty_Sold,
stock_inventory_line.product_qty AS Current_Qty,
(stock_inventory_line.product_qty / Qty_Sold) AS NOM
FROM
sale_order_line,
stock_inventory_line)
SELECT Sku, Qty_Sold, Current_Qty, NOM
FROM
cte,
product_product,
product_template,
product_category
WHERE
cte.product_id = product_product.id AND
product_product.product_tmpl_id = product_template.id AND
product_template.categ_id = product_category.id AND
product_product.default_code = cte.product_code
GROUP BY
Sku,
Current_Qty,
NOM;