如何改进 Using RANK() top 2 results into unique columns
How to improve Using RANK() top 2 results into unique columns
这里是 SQL 9(i) 代码,用于在各自的列中显示结果 1 和 2。有没有更高效的写法?
select
sc1.COIL as COIL1
, sc1.DEFECT as DEFECT1
, sc2.DEFECT as DEFECT2
FROM
(select
COIL, DEFECT
, RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
from NOVELIS.F406, NOVELIS.F408 where F406_DEFECT_CODE = F408_REJECT_CODE
GROUP BY COIL, DEFECT
)sc1
, (select
COIL, DEFECT
, RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
from NOVELIS.F406, NOVELIS.F408 where F406_DEFECT_CODE = F408_REJECT_CODE
GROUP BY COIL, DEFECT
)sc2
WHERE
sc1.RNK = 1
and sc2.RNK = 2
and sc1.COIL = sc2.COIL
您可以使用条件聚合并使用 1 个派生 table
SELECT sc1.COIL AS COIL1,
MAX(CASE WHEN RNK = 1 THEN sc1.DEFECT END) AS DEFECT1,
MAX(CASE WHEN RNK = 2 THEN sc1.DEFECT END) AS DEFECT2
FROM
(
SELECT COIL,
DEFECT,
RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
FROM NOVELIS.F406
--practice using joins
INNER JOIN NOVELIS.F408 ON F406_DEFECT_CODE = F408_REJECT_CODE
--not sure you need the group by here
) sc1
GROUP BY sc1.COIL
为避免两次阅读表格,只需阅读一次并得出结果:-
select
coil,
max (case when rnk=1 then defect else null end) defect1,
max (case when rnk=2 then defect else null end) defect2
FROM (
select
COIL, DEFECT,
RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
from NOVELIS.F406
inner join NOVELIS.F408 on F406_DEFECT_CODE = F408_REJECT_CODE
) sc
WHERE
sc.RNK <= 2
group by coil
这里是 SQL 9(i) 代码,用于在各自的列中显示结果 1 和 2。有没有更高效的写法?
select
sc1.COIL as COIL1
, sc1.DEFECT as DEFECT1
, sc2.DEFECT as DEFECT2
FROM
(select
COIL, DEFECT
, RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
from NOVELIS.F406, NOVELIS.F408 where F406_DEFECT_CODE = F408_REJECT_CODE
GROUP BY COIL, DEFECT
)sc1
, (select
COIL, DEFECT
, RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
from NOVELIS.F406, NOVELIS.F408 where F406_DEFECT_CODE = F408_REJECT_CODE
GROUP BY COIL, DEFECT
)sc2
WHERE
sc1.RNK = 1
and sc2.RNK = 2
and sc1.COIL = sc2.COIL
您可以使用条件聚合并使用 1 个派生 table
SELECT sc1.COIL AS COIL1,
MAX(CASE WHEN RNK = 1 THEN sc1.DEFECT END) AS DEFECT1,
MAX(CASE WHEN RNK = 2 THEN sc1.DEFECT END) AS DEFECT2
FROM
(
SELECT COIL,
DEFECT,
RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
FROM NOVELIS.F406
--practice using joins
INNER JOIN NOVELIS.F408 ON F406_DEFECT_CODE = F408_REJECT_CODE
--not sure you need the group by here
) sc1
GROUP BY sc1.COIL
为避免两次阅读表格,只需阅读一次并得出结果:-
select
coil,
max (case when rnk=1 then defect else null end) defect1,
max (case when rnk=2 then defect else null end) defect2
FROM (
select
COIL, DEFECT,
RANK() OVER(PARTITION BY COIL ORDER BY WEIGHT DESC) RNK
from NOVELIS.F406
inner join NOVELIS.F408 on F406_DEFECT_CODE = F408_REJECT_CODE
) sc
WHERE
sc.RNK <= 2
group by coil