Question

我有以下查询，如果表数据增长并包含数百万条记录，是否会导致性能问题？可以通过我在选择几次中选择count（）的方式来增强它吗？我已经在6列上添加了索引。 我知道连接不好我已经在增强查询

SELECT
P.CID,
P.CB,
    (SELECT COUNT(1)
    FROM EED_TABLE F
    WHERE F.ID = P.ID
    AND F.BC = P.BC
    AND F.PCD = P.PCD
    AND F.CID = P.CID
    AND F.BRC = P.BRC
    AND F.ST = 'F') ST_F,
        (SELECT COUNT(1)
        FROM EED_TABLE N
        WHERE N.ID = P.ID
        AND N.BC = P.BC
        AND N.PCD = P.PCD
        AND N.COMP_CODE = P.COMP_CODE
        AND N.BRC = P.BRC
        AND N.ST = 'N') ST_N,
            (SELECT COUNT(1)
            FROM EED_TABLE A
            WHERE A.ID = P.ID
            AND A.BC = P.BC
            AND A.PCD = P.PCD
            AND A.CID = P.CID
            AND F.BRC = P.BRC
            AND A.ST = 'A') ST_A
    FROM EED_TABLE P ,EDD_DEF D
     WHERE P.PCD = D.PCD 
   AND P.BC= D.BC
   AND P.CD= 1
   AND P.ID = 1
   AND P.BC= 22
   AND P.PCD = 31

Answer 1

我总是更愿意选择JOIN而不是选择更多的陈述，这就是我要做的事情，当然不知道你的数据所以也许它不会工作，但是给它一个机会让我知道结果和速度

  select
  p.cid, p.cb, SUM(case when f.id is not null then 1 else 0 end)  st_f,
             , SUM(case when a.id is not null then 1 else 0 end)  st_a
             , SUM(case when n.id is not null then 1 else 0 end)  st_n
  from eed_table p
           join edd_def d on p.pcd = d.pcd and p.bc = d.bc
           left join eed_table f on f.id = p.id and f.bc = p.bc
                                and f.pcd = p.pcd and f.cid = p.cid
                                and f.brc = p.brc and f.st = 'f'
           left join eed_table a on p.id = a.id and p.bc = a.bc
                                and p.pcd = a.pcd and p.cid = a.cid
                                and p.brc = a.brc and a.st = 'a'
           left join  eed_table n on n.id = p.id and n.bc = p.bc
                                 and n.pcd = p.pcd and n.comp_code = p.comp_code
                                 and n.brc = p.brc and n.st = 'n'
  where p.cd = 1 and p.id = 1 and p.bc = 22 and p.pcd = 31
  group by p.cid, p.cb

Answer 2

似乎您的查询可以使用窗口函数重写：

SELECT
    DISTINCT P.CID, P.CB
    , SUM(CASE WHEN P.ST = 'F' THEN 1 ELSE 0 END) OVER (PARTITION BY P.ID, P.BC, P.PCD, P.CID, P.BRC) ST_F
    , SUM(CASE WHEN P.ST = 'N' THEN 1 ELSE 0 END) OVER (PARTITION BY P.ID, P.BC, P.PCD, P.COMP_CODE, P.BRC) ST_N
    , SUM(CASE WHEN P.ST = 'A' THEN 1 ELSE 0 END) OVER (PARTITION BY P.ID, P.BC, P.PCD, P.CID, P.BRC) ST_A
FROM
    EED_TABLE P
WHERE
    P.CD = 1
    AND P.ID = 1
    AND P.BC = 22
    AND P.PCD = 31
    AND EXISTS (SELECT 1 FROM EDD_DEF D WHERE P.PCD = D.PCD AND P.BC= D.BC)

select中的几个选择计数可以增强吗？

2 个答案: