我无法弄清楚如何为MySQL子查询设置正确的索引

Question

这是我的问题：

SELECT IFNULL(d_source,"TOTAL") AS SOURCE
    , IFNULL(SUM(STORECOUNT),0) AS STORECOUNT
    , IFNULL(SUM(STORECOUNTCP),0) AS STORECOUNTCP
    , IFNULL(SUM(TDP),0) AS TDP
    , IFNULL(SUM(TDPCP),0) AS TDPCP
    , IFNULL(ROUND(SUM(TDP) / SUM(STORECOUNT),2),0) AS AVGUPCSPERSTORE
    , IFNULL(ROUND(SUM(TDPCP) / SUM(STORECOUNTCP),2),0) AS AVGUPCSPERSTORECP
    , IFNULL(ROUND(SUM(TOTAL) / SUM(STORECOUNT) / 8.57,2),0) AS AVGUNITSPERSTORE
    , IFNULL(ROUND(SUM(CPTOTAL) / SUM(STORECOUNTCP) / 4.29,2),0) AS AVGUNITSPERSTORECP
    , IFNULL(ROUND(SUM(TOTAL),0),0) AS TOTAL
    , IFNULL(ROUND(SUM(CPTOTAL),0),0) AS CPTOTAL
    , IFNULL(ROUND(SUM(PPTOTAL),0),0) AS PPTOTAL
    ,  ROUND(sum(2016_Apr),0) AS 2016_Apr , ROUND(sum(2016_May),0) AS 2016_May  
FROM (
    SELECT d_source
        ,key_retailer
        ,COUNT(DISTINCT(CASE WHEN datetimesql BETWEEN '2016-04-01' AND '2016-05-31' AND unit_sales > 0 THEN store_id  END)) STORECOUNT
        ,COUNT(DISTINCT(CASE WHEN datetimesql BETWEEN '2016-05-01' AND '2016-05-31' AND unit_sales > 0 THEN store_id END)) STORECOUNTCP
        ,COUNT(DISTINCT(CASE WHEN datetimesql BETWEEN '2016-04-01' AND '2016-05-31' AND unit_sales > 0 THEN CONCAT(upc,store_id) END)) TDP
        ,COUNT(DISTINCT(CASE WHEN datetimesql BETWEEN '2016-05-01' AND '2016-05-31' AND unit_sales > 0 THEN CONCAT(upc,store_id) END)) TDPCP
        ,SUM(CASE WHEN datetimesql BETWEEN '2016-04-01' AND '2016-05-31' THEN unit_sales  ELSE 0 END) TOTAL
        ,SUM(CASE WHEN datetimesql BETWEEN '2016-05-01' AND '2016-05-31' THEN unit_sales  ELSE 0 END) CPTOTAL
        ,SUM(CASE WHEN datetimesql BETWEEN '2016-04-01' AND '2016-04-30' THEN unit_sales  ELSE 0 END) PPTOTAL
        ,SUM(CASE WHEN datetimesql BETWEEN '2016-04-01' AND '2016-04-30' THEN unit_sales ELSE 0 END) 2016_Apr 
        ,SUM(CASE WHEN datetimesql BETWEEN '2016-05-01' AND '2016-05-31' THEN unit_sales ELSE 0 END) 2016_May  
    FROM storeCheckRecords   
        INNER JOIN allStores ON allStores.id = store_id  
    WHERE d_source !='STORELOCATOR' 
    GROUP BY d_source
    ) T 
GROUP BY d_source WITH ROLLUP

以下是解释：

id  s_type   table       type   p_keys    key     key_len  ref      rows         Extra
1   PRIMARY  <derived2>  ALL    NULL      NULL    NULL     NULL     2            Using filesort
2   DERIVED  SCR         ALL    store_id  NULL    NULL     NULL     1229950      Using where; Using filesort
2   DERIVED allStores    eq_ref PRIMARY   PRIMARY 4        dfc.SCR  1            Using where

我不明白我缺少什么来停止搜索整个SCR表并对其进行索引以便它不会搜索所有SCR表。感谢您的帮助。