SQL：如何找到类型为 varchar2 的最大时间

Question

我有一个问题，我必须从周末最晚开张的商店 table 中查找商店的详细信息。在商店 table 中，我有一个名为 weekendHours 的属性，类型为 varchar2，示例是：(10:00 am - 5:00pm)。我试过 To_char( S.WeekendHours=max(S.WeekendHours ); 但它不起作用！我该怎么做？

Answer 1

如果你想要最新开的店，那么你可以这样做：

select t.*
from t
order by t.weekendhours desc
fetch first 1 row only;

但是，对于您的时间格式，这将不起作用，因为 2:00 a.m。将在 1:00 p.m.

之后

因此，您需要将范围转换为时间。这是一种方法：

select t.*
from t
order by cast(substring(t.weekendhours, 1, 8) as time) desc
fetch first 1 row only;

当然，这些查询使用跨许多数据库的通用方法。该逻辑可能适用于您的数据库，但语法可能不同。

注意：所有这些都是因为 weekendhours 列已损坏。它应该在两列中，weekend_opentime 和 weekend_closetime。那么查询将是微不足道的。

Answer 2

您可以使用正则表达式提取打开和关闭时间，然后根据需要对其进行操作：

SELECT s.*,
       TRIM(REGEXP_SUBSTR(s.weekend_hours, '[0-9]+:*[0-9]* *(am|pm)*', 1, 1)) AS OPENING_HOUR_STRING,
       TRIM(REGEXP_SUBSTR(s.weekend_hours, '[0-9]+:*[0-9]* *(am|pm)*', 1, 2)) AS CLOSING_HOUR_STRING
      FROM STORE s

一旦你有了上面的基本信息，你就可以操作它来获取作为日期的开盘和收盘时间，然后在适当的字段上使用 MAX：

WITH cteSTORE_STRING_VALUES AS
       (SELECT s.*,
               TRIM(REGEXP_SUBSTR(s.weekend_hours, '[0-9]+:*[0-9]* *(am|pm)*', 1, 1)) AS OPENING_HOUR_STRING,
               TRIM(REGEXP_SUBSTR(s.weekend_hours, '[0-9]+:*[0-9]* *(am|pm)*', 1, 2)) AS CLOSING_HOUR_STRING
          FROM STORE s),
     cteALL_STORE_VALUES AS
       (SELECT s.*,
               CASE
                 WHEN LENGTH(OPENING_HOUR_STRING) < 4 THEN LPAD(OPENING_HOUR_STRING, 4, '0')
                 ELSE OPENING_HOUR_STRING
               END AS PADDED_OPENING_STRING,
               CASE
                 WHEN LENGTH(CLOSING_HOUR_STRING) < 4 THEN LPAD(CLOSING_HOUR_STRING, 4, '0')
                 ELSE CLOSING_HOUR_STRING
               END AS PADDED_CLOSING_STRING
          FROM cteSTORE_STRING_VALUES s),
     cteSTORES_WITH_HOURS AS
       (SELECT a.*,
               CASE
                 WHEN UPPER(SUBSTR(a.OPENING_HOUR_STRING, -3)) IN (' AM', ' PM') THEN
                   TO_DATE(a.OPENING_HOUR_STRING, 'HH:MI AM')
                 WHEN UPPER(SUBSTR(a.OPENING_HOUR_STRING, -2)) IN ('AM', 'PM') THEN
                   TO_DATE(a.OPENING_HOUR_STRING, 'HH:MIAM')
                 WHEN INSTR(a.OPENING_HOUR_STRING, ':') > 0 THEN
                   TO_DATE(a.OPENING_HOUR_STRING, 'HH24:MI')
                 ELSE
                   TO_DATE(a.PADDED_OPENING_STRING, 'HH24MI')
               END AS OPENING_HOURS,
               CASE
                 WHEN UPPER(SUBSTR(a.CLOSING_HOUR_STRING, -3)) IN (' AM', ' PM') THEN
                   TO_DATE(a.CLOSING_HOUR_STRING, 'HH:MI AM')
                 WHEN UPPER(SUBSTR(a.CLOSING_HOUR_STRING, -2)) IN ('AM', 'PM') THEN
                   TO_DATE(a.CLOSING_HOUR_STRING, 'HH:MIAM')
                 WHEN INSTR(a.CLOSING_HOUR_STRING, ':') > 0 THEN
                   TO_DATE(a.CLOSING_HOUR_STRING, 'HH24:MI')
                 ELSE
                   TO_DATE(a.PADDED_CLOSING_STRING, 'HH24MI')
               END AS CLOSING_HOURS
          FROM cteALL_STORE_VALUES a)
SELECT *
  FROM cteSTORES_WITH_HOURS
  WHERE OPENING_HOURS = (SELECT MAX(OPENING_HOURS)
                           FROM cteSTORES_WITH_HOURS);

SQLFiddle here

祝你好运。

SQL：如何找到类型为 varchar2 的最大时间

SQL : how to find max time where its type is varchar2

sql

oracle

to-char