Question

I am trying to do all of these SELECT statements in all one query so I will be able to further it and group it. I believe I have to tell it to JOIN on TABLE1. I can tell you that it should be JOINing on the field called ITEM. I have tried dozens of JOIN statements none of which does the trick because I have two WHERE statements in my subqueries.

SELECT ITEM, DSI, LEADTIME,
(SELECT COUNT(ORDER_NUMBER) FROM SUBTABLE1 TR1 WHERE TRANS_DATE BETWEEN DATE_SUB(curdate(), INTERVAL 730 DAY) AND DATE_SUB(curdate(), INTERVAL 365 DAY))
as OLDORDERS,
(SELECT COUNT(ORDER_NUMBER) FROM SUBTABLE2 TR2 WHERE TRANS_DATE BETWEEN DATE_SUB(curdate(), INTERVAL 364 DAY) AND curdate())
as NEWORDERS
FROM TABLE1

Displays:

ITEM   |  DSI  |  LEADTIME  | OLDORDERS | NEWORDERS
PROD-1    0         1          16036      38399
PROD-2    1         0          16036      38399
PROD-3    1         1          16036      38399

Again…I believe I need it to JOIN the field ITEM on the subqueries, but I do not know how to do this, any ideas?

Answer 1

You don’t actually need a JOIN, per se; rather, you need to “correlate” your subqueries, so that they refer to data in their containing query.

You haven’t given your exact table definitions, so I can’t say for sure, but here’s my guess at what you need:

SELECT item, dsi, leadtime,
       ( SELECT COUNT(order_number)
           FROM subtable1
          WHERE trans_date BETWEEN DATE_SUB(CURDATE(), INTERVAL 730 DAY)
                               AND DATE_SUB(CURDATE(), INTERVAL 365 DAY)
                -- restrict to "current" record from TABLE1:
            AND subtable1.item = table1.item
       ) as OLDORDERS,
       ( SELECT COUNT(order_number)
           FROM subtable1
          WHERE trans_date BETWEEN DATE_SUB(CURDATE(), INTERVAL 364 DAY)
                               AND CURDATE()
                -- restrict to "current" record from table1:
            AND subtable1.item = table1.item
       ) as NEWORDERS
  FROM table1
;

That’s assuming that table1.item is the primary key, and that subtable1.item is a foreign-key referring to it. Naturally you’ll have to adjust the query if that’s not the case.