Complex Case Statement Issue - Oracle SQL - sql

Question

Wrote the query below, but am getting multiplied amounts because the aggregation needs to occur before the case statements. Would love some advice on the best way to structure this.
Select Store, CUSTID, CUST.ID_CUST,
Sum(
CASE
WHEN Cust_Gift.Code_Status = 'C' AND Gift_Item.FLAG_STORE_LOC = 'N'
THEN Cust_Gift.AMT_PAID ELSE 0
END) GiftAmt,
Sum(
CASE WHEN Cust_Gift.Code_Status = 'C' AND Gift_Item.FLAG_STORE_LOC = 'Y'
THEN Cust_Gift.AMT ELSE 0
END) CustGiftAmt,
Sum(
CASE WHEN Cust_Coupon.Code_Status = 'C'
THEN Cust_Coupon.AMT
ELSE 0
END) CouponAmt,
Sum(CASE WHEN Cust_Sports.Status = 'C'
THEN Cust_Sports.AMT
ELSE 0
END) SportsAmt
FROM CUST
LEFT OUTER JOIN CUST_GIFT
ON CUST.ID_CUST = CUST_GIFT.ID_CUST
LEFT OUTER JOIN CUST_COUPON
ON CUST.ID_CUST = CUST_COUPON.ID_CUST
LEFT OUTER JOIN CUST_SPORTS
ON CUST.ID_CUST = CUST_SPORTS.ID_CUST
INNER JOIN GIFT_ITEM
ON CUST_GIFT.ID_GIFT_ITEM = GIFT_ITEM.ID_GIFT_ITEM
WHERE (STORE = 'M669098' OR STORE = 'M66923434' )
Group by CustID, Store, CUST.ID_CUST

Answer 1

This is one way you could do it:
SELECT cust.store,
cust.custid,
cust.id_cust,
gift.giftamt,
gift.custgift,
cpn.couponamt,
sprt.sportsamt
FROM cust
LEFT OUTER JOIN (SELECT id_cust,
SUM(CASE WHEN cg.code_status = 'C' AND gi.flag_store_loc = 'N' THEN cg.amt_paid END) giftamt,
SUM(CASE WHEN cg.code_status = 'C' AND gi.flag_store_loc = 'Y' THEN cg.amt_paid END) custgiftamt
FROM cust_gift cg
INNER JOIN gift_item gi ON cg.id_gift_item = gi.id_gift_item) gift ON cust.id_cust = gift.id_cust
LEFT OUTER JOIN (SELECT id_cust,
SUM(CASE WHEN code_status = 'C' THEN amt END) couponamt
FROM cust_coupon) cpn ON cust.id_cust = cpn.id_cust
LEFT OUTER JOIN (SELECT id_cust,
SUM(CASE WHEN status = 'C' THEN amt END) sportsamt
FROM cust_sports) sprt ON cust.id_cust = sprt.id_cust
WHERE (STORE = 'M669098' OR STORE = 'M66923434');