Question

我需要重写以下查询以避免子查询。我该怎么做....下面的查询中有两个子查询

select  
  cc1.claimid as claimid,
  cc1.createdate as createdate,
  cc1.condcode as condition_cd1,
  cc2.condcode as condition_cd2,
  cc3.condcode as condition_cd3

from claimcond cc1 (nolock)
left outer join claimcond cc2 (nolock) on 
cc1.claimid = cc2.claimid 
and cc2.condcode = (select min(condcode) from claimcond cc (nolock) where cc1.claimid = cc.claimid)
and cc1.condcode <> cc2.condcode

left outer join claimcond cc3 (nolock) on 
cc1.claimid = cc3.claimid 
and cc3.condcode in (select min(condcode) from claimcond cc (nolock) where cc1.claimid = cc.claimid 
and ((cc.condcode > cc2.condcode)))
and cc1.condcode <> cc3.condcode

ORDER BY cc1.claimid, cc1.condcode DESC

Answer 1

存在：

select  
  cc1.claimid as claimid,
  cc1.createdate as createdate,
  cc1.condcode as condition_cd1,
  cc2.condcode as condition_cd2,
  cc3.condcode as condition_cd3

from claimcond cc1 (nolock)
left outer join claimcond cc2 (nolock) on 
cc1.claimid = cc2.claimid 
and cc1.condcode <> cc2.condcode

left outer join claimcond cc3 (nolock) on 
cc1.claimid = cc3.claimid 

and ((cc.condcode > cc2.condcode)))
and cc1.condcode <> cc3.condcode
WHERE EXISTS (
    SELECT '1'
    FROM claimcond cc (nolock)
    WHERE cc1.claimid = cc.claimid and -- Maybe OR 
          cc2.claimID = cc.claimid )

ORDER BY cc1.claimid, cc1.condcode DESC

Answer 2

你应该看看它的表现如何：

DECLARE @MinCondCode TABLE (
    claimid INT,                --datatype correct?
    MinCode1 VARCHAR(20) NULL,  --datatype correct?
    MinCode2 VARCHAR(20) NULL   --datatype correct?
)

INSERT INTO @MinCondCode (claimid,MinCode1)
    select claimid,min(condcode)
    from claimcond cc (nolock)
    group by claimid

UPDATE MinCondCode
SET MinCode2=(
    select min(condcode)
    from claimcond cc (nolock)
    WHERE cc.condcode > MinCondCode.MinCode1
    AND MinCondCode.claimid = cc.claimid 
)

select  
  cc1.claimid as claimid,
  cc1.createdate as createdate,
  cc1.condcode as condition_cd1,
  cc2.condcode as condition_cd2,
  cc3.condcode as condition_cd3
from claimcond cc1 (nolock)
INNER JOIN @MinCondCode mn on mn.claimid=cc1.claimid
left outer join claimcond cc2 (nolock) on cc1.claimid = cc2.claimid 
    and cc2.condcode = mn.MinCode1
    and cc1.condcode <> cc2.condcode
left outer join claimcond cc3 (nolock) on cc1.claimid = cc3.claimid 
    and cc3.condcode = mn.MinCode2
    and cc1.condcode <> cc3.condcode
ORDER BY cc1.claimid, cc1.condcode DESC

重写查询以避免子查询

2 个答案: