我有一个DB2表,其中一列(A)的值为PQR或XYZ,我需要输出基于Col C日期的最新两条记录的值A=PQR。
我需要输出基于Col C日期的最新两条记录的值A = PQR。
示例表
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,我的输出将是马克和克雷格的记录。
你可以使用 nth_value
OLAP功能。OLAP规格.
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。
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;
一个简单的解决办法是
SELECT A,B,C
FROM tab
WHERE A = 'PQR'
ORDER BY C DESC FETCH FIRST 2 ROWS only