我有一个DB2表,其中一列(a(的值为PQR或XYZ。
我需要基于C列日期的最新两条记录的值A=PQR的输出。
样品台
A B C
--- ----- ----------
PQR Mark 08/08/2019
PQR Mark 08/01/2019
XYZ Mark 07/01/2019
PQR Joe 10/11/2019
XYZ Joe 10/01/2019
PQR Craig 06/06/2019
PQR Craig 06/20/2019
在这个示例表中,我的输出将是Mark和Craig记录的
自11.1起
您可以使用nth_value
OLAP函数。请参阅OLAP规范。
SELECT A, B, C
FROM
(
SELECT
A, B, C
, NTH_VALUE (A, 1) OVER (PARTITION BY B ORDER BY C DESC ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) C1
, NTH_VALUE (A, 2) OVER (PARTITION BY B ORDER BY C DESC ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) C2
FROM TAB
)
WHERE C1 = 'PQR' AND C2 = 'PQR'
dbfiddle链接。
旧版本
SELECT T.*
FROM TAB T
JOIN
(
SELECT B
FROM
(
SELECT
A, B
, ROWNUMBER() OVER (PARTITION BY B ORDER BY C DESC) RN
FROM TAB
)
WHERE RN IN (1, 2)
GROUP BY B
HAVING MIN(A) = MAX(A) AND COUNT(1) = 2 AND MIN(A) = 'PQR'
) G ON G.B = T.B;
是一个简单的解决方案
SELECT A,B,C
FROM tab
WHERE A = 'PQR'
ORDER BY C DESC FETCH FIRST 2 ROWS only