Question

我有一个问题，我必须从商店表中查找商店的详细信息，该商品表会在周末打开最新商品。在商店表中，我有一个名为weekendHours的属性，其类型为varchar2，示例为:(上午10:00 - 下午5:00）。我试过了 To_char（S.WeekendHours = max（S.WeekendHours）; 但它不起作用!! 我怎么能这样做？

Answer 1

如果您想要打开最新的商店，那么您可以想到：

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

但是，使用您的时间格式，这将无效，因为凌晨2点将在下午1点之后。

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，这些查询在许多数据库中使用通用方法。逻辑可能适用于您的数据库，但语法可能不同。

注意：所有这一切都是因为列weekendhours已损坏。它应该分为两列，weekend_opentime和weekend_closetime。然后查询将是微不足道的。

Answer 2

您可以使用正则表达式提取开始和结束时间，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

获得上述基本信息后，您可以对其进行操作以获得日期的开始和结束时间，然后在相应的字段上使用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：如何查找其类型为varchar2的最大时间

2 个答案: