两个sql,很简单的语法
高手帮看看两个哪个更快,为什么
thx~SELECT T1.*,T2.A2 AS A3 FROM qqqqqqqqqqqqqq T1
LEFT JOIN (SELECT MIN(A1) AS A1,A2 FROM qqqqqqqqqqqqqq T1
GROUP BY A2)T2 ON T2.A1=T1.A1SELECT T1.*,T2.A2 AS A3 FROM qqqqqqqqqqqqqq T1
LEFT JOIN (SELECT A1,A2 FROM
(SELECT *,ROW_NUMBER() OVER (PARTITION BY A2 ORDER BY A1) AS 'RowNumber'
FROM qqqqqqqqqqqqqq)RR
WHERE RR.ROWNUMBER=1)T2 ON T2.A1=T1.A1
高手帮看看两个哪个更快,为什么
thx~SELECT T1.*,T2.A2 AS A3 FROM qqqqqqqqqqqqqq T1
LEFT JOIN (SELECT MIN(A1) AS A1,A2 FROM qqqqqqqqqqqqqq T1
GROUP BY A2)T2 ON T2.A1=T1.A1SELECT T1.*,T2.A2 AS A3 FROM qqqqqqqqqqqqqq T1
LEFT JOIN (SELECT A1,A2 FROM
(SELECT *,ROW_NUMBER() OVER (PARTITION BY A2 ORDER BY A1) AS 'RowNumber'
FROM qqqqqqqqqqqqqq)RR
WHERE RR.ROWNUMBER=1)T2 ON T2.A1=T1.A1
SELECT T1.*
,case when not exists (
select 1
from qqqqqqqqqqqqqq T2
where T2.A1<T1.A1
and T2.A2 = T1.A2
) then T2.A2 else NULL end AS A3
FROM qqqqqqqqqqqqqq T1
SELECT T1.*
,case when not exists (
select 1
from qqqqqqqqqqqqqq T2
where T2.A1<T1.A1
and T2.A2 = T1.A2
) then T1.A2 else NULL end AS A3
FROM qqqqqqqqqqqqqq T1
thx