MYSQL Query with conditional statement

SELECT
p.pcode,
p.productName,
CASE gr_rows = 0 AND sl_rows = 0
THEN opening_stock = 0
CASE gr_rows > 0 AND sl_rows = 0
THEN opening_stock = received_stock
CASE gr_rows > 0 AND sl_rows > 0
THEN opening_stock = opening_stock
opening_stock,received_stock,sold_stock
FROM tbl_products p
LEFT JOIN (
    SELECT COUNT(r.ID) AS gr_rows,r.pcode,r.received_on,SUM(r.received_qty) AS received_stock
    FROM tbl_shop_gr_items r
    WHERE r.received_on = '2019-10-02'
    GROUP BY r.pcode
)AS r ON p.pcode = r.pcode
LEFT JOIN (
    SELECT COUNT(s.ID) AS sl_rows,s.pcode,s.date_created,SUM(s.soldQty) AS sold_stock
    FROM tbl_sold_items s
    WHERE s.date_created = '2019-10-02'
    GROUP BY s.pcode
)AS s ON p.pcode = s.pcode
LEFT JOIN (
    SELECT t.ID,t.pcode,t.date_created,t.remaining_qty AS opening_stock
    FROM tbl_sold_items t
    WHERE t.date_created = '2019-10-02'
    GROUP BY t.pcode ORDER BY t.ID DESC LIMIT 1
)AS t ON p.pcode = t.pcode