Question

我需要从现在开始过去10天我目前有以下Oracle sql查询来获取最近10个日期。

WITH DATES AS (
  SELECT sysdate - 10 AS value_date FROM dual
  UNION
  SELECT sysdate - 9  AS value_date FROM dual
  UNION
  SELECT sysdate - 8  AS value_date FROM dual
  UNION
  SELECT sysdate - 7  AS value_date FROM dual
  UNION
  SELECT sysdate - 6  AS value_date FROM dual
  UNION
  SELECT sysdate - 5  AS value_date FROM dual
  UNION
  SELECT sysdate - 4  AS value_date FROM dual
  UNION
  SELECT sysdate - 3  AS value_date FROM dual
  UNION
  SELECT sysdate - 2  AS value_date FROM dual
  UNION
  SELECT sysdate - 1  AS value_date FROM dual
  UNION
  SELECT sysdate      AS value_date FROM dual
  UNION
  SELECT sysdate + 1  AS value_date FROM dual

但我想要一个更合适有效的方法来获得过去的10个日期。 Union查询看起来很脏。我如何在Oracle SQL中执行此操作？

Answer 1

使用与CONNECT BY子句更紧凑的等效项：

SELECT trunc( sysdate ) - level + 2
FROM dual
CONNECT BY rownum <= 12

演示：http://sqlfiddle.com/#!4/a50e25/5

| TRUNC(SYSDATE)-LEVEL+2 |
|------------------------|
|   2017-09-15T00:00:00Z |
|   2017-09-14T00:00:00Z |
|   2017-09-13T00:00:00Z |
|   2017-09-12T00:00:00Z |
|   2017-09-11T00:00:00Z |
|   2017-09-10T00:00:00Z |
|   2017-09-09T00:00:00Z |
|   2017-09-08T00:00:00Z |
|   2017-09-07T00:00:00Z |
|   2017-09-06T00:00:00Z |
|   2017-09-05T00:00:00Z |
|   2017-09-04T00:00:00Z |

Answer 2

您可以使用分层查询获得与查询相同的结果（也使用TRUNC()将日期截断为当天开始的午夜）：

SELECT TRUNC( SYSDATE ) - 11 + LEVEL
FROM   DUAL
CONNECT BY LEVEL <= 12

或者，使用递归子查询分解子句：

WITH days ( dt ) AS (
  SELECT TRUNC( SYSDATE ) - 10 FROM DUAL
UNION ALL
  SELECT dt + 1 FROM days WHERE dt <= SYSDATE
)
SELECT dt FROM days

Oracle获得最近10天的sql

2 个答案: