在 Oracle SQL 中计算一年中的手动周数答案

【问题标题】：Calculate manual week number of year in Oracle SQL在 Oracle SQL 中计算一年中的手动周数
【发布时间】：2020-02-18 06:28:29
【问题描述】：

我有一个日期列，并且我需要在 oracle 中计算他们一年中的周数的另一列，周数应该是从星期日到星期六，从一年的第一天开始。

以当年为例

Week 1 : 1 Jan 2020 (Wednesday) - 4 Jan 2020(Saturday)


Week 2 : 5 Jan 2020 (Sunday)        - 11 Jan 2020(Saturday)

. . . . .


Week 5 : 26 Jan 2020 (Sunday) - 1 Feb 2020 (Saturday)

等等……

【问题讨论】：

您的要求是否灵活？如果您使用 ISO 8601 标准周数，这个问题会简单得多：select to_char(sysdate, 'IW') from dual;。

标签： sql oracle

【解决方案1】：

您需要使用层次结构查询编写自己的逻辑。

类似于以下内容：

SQL> SELECT WEEKNUMBER,
  2  WEEK_START,
  3  CASE WHEN WEEKNUMBER = 1 THEN FIRST_WEEKEND ELSE WEEK_START + 6 END AS WEEK_END
  4  FROM
  5  (SELECT
  6      CASE
  7          WHEN LEVEL = 1 THEN FIRST_DAY
  8          ELSE FIRST_WEEKEND + ( LEVEL - 2 ) * 7 + 1
  9      END AS WEEK_START,
 10      FIRST_WEEKEND,
 11      LEVEL AS WEEKNUMBER
 12  FROM
 13      ( SELECT
 14              TRUNC(SYSDATE, 'YEAR') FIRST_DAY,
 15              NEXT_DAY(TRUNC(SYSDATE, 'YEAR'), 'SATURDAY') FIRST_WEEKEND
 16          FROM DUAL )
 17  CONNECT BY
 18      CASE WHEN LEVEL = 1 THEN FIRST_DAY
 19          ELSE FIRST_WEEKEND + ( LEVEL - 2 ) * 7 + 1
 20      END < ADD_MONTHS(TRUNC(SYSDATE, 'YEAR'), 12));

WEEKNUMBER WEEK_STAR WEEK_END
---------- --------- ---------
         1 01-JAN-20 04-JAN-20
         2 05-JAN-20 11-JAN-20
         3 12-JAN-20 18-JAN-20
         4 19-JAN-20 25-JAN-20
         5 26-JAN-20 01-FEB-20
         6 02-FEB-20 08-FEB-20
         7 09-FEB-20 15-FEB-20
         8 16-FEB-20 22-FEB-20
         9 23-FEB-20 29-FEB-20
        10 01-MAR-20 07-MAR-20
        11 08-MAR-20 14-MAR-20
        .......
        .......
        53 27-DEC-20 02-JAN-21

干杯！！

【讨论】：

【解决方案2】：

另一种选择是

with t as
(
 select trunc(sysdate,'yyyy')+level-1 as day, to_char(trunc(sysdate,'yyyy')+level-1,'DY','NLS_DATE_LANGUAGE=AMERICAN') as weekday, level - 1 as lvl
   from dual
 connect by level <= 366
), t1 as
(
select case
         when lvl = 0 then
          day
         else
          case
            when weekday = 'SUN' then
             day
          end
       end as day1,       
       lvl
  from t
), t2 as
(
select case
         when weekday = 'SAT' then
          day
       end as day2,
       lvl
  from t
)
select concat( 'Week ', wk1) as week, day1, day2  
  from 
  (
   select row_number() over (order by lvl) wk1, day1
     from t1 where day1 is not null ) t1 
  left join    
  (
   select row_number() over (order by lvl) wk2, day2
     from t2 where day2 is not null ) t2  
    on wk2 = wk1

通过使用select .. from dual connect by level 语法和case..when 表达式来扫描所有当前年份。

Demo

【讨论】：