错误代码1054交叉连接上的未知列

Question

I have three tables item , store and stock_movement . The stock movement has the fields id , item_id , store_id and quantity . I would like to create a view showing the sum of the quantities of each item in each store. If there is no stock_movement entry for an item in a store, the quantity should be zero.

I came up with the following query:

SELECT item.*, store.id, SUM(s.quantity) AS quantity
FROM item, store 
LEFT JOIN stock_movement s ON s.item_id = item.id AND store.id = s.store_id
GROUP BY store.id, item.id;

I get the following error:

Error Code: 1054 Unknown column 'item.id' in 'on clause'

If I switch the query to use FROM store, item the unknown column changes:

Error Code: 1054 Unknown column 'store.id' in 'on clause'

This answer to use INNER JOIN won't work for me since there are some items and stores without corresponding stock_movement entries ie the result is missing a few rows.

So is there a way to do this cross join?

Answer 1

You need to explicitly define your cross join :

select i.id, s.id, coalesce(sum(si.quantity),0) quantity
from store s 
  cross join item i 
  left join storeitem si on s.id = si.storeid and i.id = si.itemid
group by i.id, s.id

• SQL Fiddle Demo

BTW -- by doing it this way, you are creating a cartesian product -- all stores have all items.