Question

我想合并日期＆amp;时间。我用过'CONCAT＆＃39;功能与也＆＃39; ||＆＃39;功能。但是这两个函数花费更多次并且查询速度非常慢。有人能告诉我如何缩短查询时间吗？＆安培;什么功能可用于合并日期和＆amp;时间？谢谢你的帮助。

    where CONCAT (TO_CHAR (Date, 'YYYYMMDD'), LPAD (Time, 6, 0))
between CONCAT ('20180215', '130528') AND CONCAT ('20180215', '133003')

Answer 1

您无需将日期转换为字符串 - 只需将静态值转换为日期：

WHERE "Date" BETWEEN TO_DATE( '20180215130528', 'YYYYMMDDHH24MISS' )
                 AND TO_DATE( '20180215133003', 'YYYYMMDDHH24MISS' )

如果您想使用CONCAT，那么：

WHERE "Date" BETWEEN TO_DATE( CONCAT( '20180215', '130528' ), 'YYYYMMDDHH24MISS' )
                 AND TO_DATE( CONCAT( '20180215', '133003' ), 'YYYYMMDDHH24MISS' )

您还可以使用TIMESTAMP字面值：

WHERE "Date" BETWEEN TIMESTAMP '2018-02-15 13:05:28'
                 AND TIMESTAMP '2018-02-15 13:30:03'

Answer 2

您希望在日期上设置索引以加快查询速度更好的方法是将日期和时间合并到一个字段Date中，类型为Date（并且在Date上有索引）。这将为您提供简单的高性能查询：

WHERE Date between to_date('20180215' || '130528', 'YYYYMMDDHH24MISS') and to_date('20180215'||'133003', 'YYYYMMDDHH24MISS')

对于您当前的方案，您将获得更好的性能结构，如下所示：

where Date between to_date('20180215', 'YYYYMMDD') and to_date('20180215', 'YYYYMMDD') and Date || LPAD (Time, 6, 0)) between CONCAT ('20180215', '130528') AND CONCAT ('20180215', '133003')

将日期和时间组合到日期时间

2 个答案: