Question

我有一列以{LossDate）格式保存yyyymmdd。我需要验证如果该月在30天内结束，那么没有报告损失日期为31的损失。我有数百万条记录。非常感谢您的帮助。

LossDate
--------
20120128
20150520
20180631

查询应返回最后一个无效记录，因为200806在30天内结束。

Answer 1

您可以在下面创建一个ISDATE函数，然后在诸如SELECT * FROM TABLE WHERE DB_IS_DATE(LOSSDATE) = 0之类的查询中使用它来查找所有无效日期

CREATE OR REPLACE FUNCTION IS_DATE(YYYYMMDD INTEGER)
RETURNS SMALLINT
LANGUAGE SQL CONTAINS SQL DETERMINISTIC NO EXTERNAL ACTION
RETURN
  CASE
    WHEN YYYYMMDD/10000 BETWEEN 1 AND 9999
    AND(    ( MOD(YYYYMMDD/100, 100) IN (1,3,5,7,8,10,12) AND MOD(YYYYMMDD,100) BETWEEN 1 AND 31 )  -- Jan,Mar,May,Jul,Aug,Oct,Dec have 31 days
         OR ( MOD(YYYYMMDD/100, 100) IN (4,6,9,11)        AND MOD(YYYYMMDD,100) BETWEEN 1 AND 30 )  -- Apr,Jun,Sep,Nov             have 30 days
         OR ( MOD(YYYYMMDD/100, 100) = 2                  AND MOD(YYYYMMDD,100) BETWEEN 1 AND 28 )  -- Feb has 28 days
         OR ( MOD(YYYYMMDD/100, 100) = 2                  AND MOD(YYYYMMDD,100) BETWEEN 1 AND 29    --   unless is a leap year. i.e.
              AND ( ( MOD(YYYYMMDD/10000,4) = 0 AND MOD(YYYYMMDD/10000,100) <> 0)                   --   year is divisable by 4 but not 100
                OR  MOD(YYYYMMDD/10000,400) = 0 )                                                   --     or year is divisable by 400
            )       
         )
    THEN 1
    ELSE 0
  END

如果您正在使用Db2 Warehouse，则可以从函数中返回BOOLEAN。例如

CREATE OR REPLACE FUNCTION IS_DATE(YYYYMMDD INTEGER)
RETURNS BOOLEAN
LANGUAGE SQL CONTAINS SQL DETERMINISTIC NO EXTERNAL ACTION
RETURN
        YYYYMMDD/10000 BETWEEN 1 AND 9999
    AND(    ( MOD(YYYYMMDD/100, 100) IN (1,3,5,7,8,10,12) AND MOD(YYYYMMDD,100) BETWEEN 1 AND 31 )  -- Jan,Mar,May,Jul,Aug,Oct,Dec have 31 days
         OR ( MOD(YYYYMMDD/100, 100) IN (4,6,9,11)        AND MOD(YYYYMMDD,100) BETWEEN 1 AND 30 )  -- Apr,Jun,Sep,Nov             have 30 days
         OR ( MOD(YYYYMMDD/100, 100) = 2                  AND MOD(YYYYMMDD,100) BETWEEN 1 AND 28 )  -- Feb has 28 days
         OR ( MOD(YYYYMMDD/100, 100) = 2                  AND MOD(YYYYMMDD,100) BETWEEN 1 AND 29    --   unless is a leap year. i.e.
              AND ( ( MOD(YYYYMMDD/10000,4) = 0 AND MOD(YYYYMMDD/10000,100) <> 0)                   --   year is divisable by 4 but not 100
                OR  MOD(YYYYMMDD/10000,400) = 0 )                                                   --     or year is divisable by 400
            )       
         )

该函数可用于将输入转换为DATE（如果它是有效日期）。例如

SELECT i, IS_DATE(i) AS IS_DATE
,      CASE WHEN IS_DATE(i) = 1 THEN DATE(TO_DATE(DIGITS(DECIMAL(i,8,0)),'YYYYMMDD')) END AS DATE
FROM TABLE(VALUES(-999),(0),(1),(00010101),(99991231),(20180101),(20180228),(20160229),(20180229),(20000229),(19000229)) as D(i)

返回

 I        IS_DATE DATE
 -------- ------- ----------
     -999       0 NULL
        0       0 NULL
        1       0 NULL
    10101       1 0001-01-01
 99991231       1 9999-12-31
 20180101       1 2018-01-01
 20180228       1 2018-02-28
 20160229       1 2016-02-29
 20180229       0 NULL
 20000229       1 2000-02-29
 19000229       0 NULL

该函数还将接受“ YYYYMMDD”格式的字符串。 db2将为您将字符串转换为整数。如果您有一个字符串例如“ YYYY-MM-DD”格式，则可以创建调用上述函数的函数的字符版本，例如

CREATE OR REPLACE FUNCTION IS_DATE(YYYYMMDD VARCHAR(10))
RETURNS INTEGER
LANGUAGE SQL CONTAINS SQL DETERMINISTIC NO EXTERNAL ACTION
RETURN
   CASE WHEN REGEXP_LIKE(YYYYMMDD,'[0-9]{4}?-[0-9]{2}?-[0-9]{2}?') = 1 
        THEN IS_DATE(INTEGER(REPLACE(YYYYMMDD,'-',''))) ELSE 0 END

;

Answer 2

对于您的特定问题，以下内容将返回错误的行：

select * 
from table 
where substr(lossdate,5,2) in ('04','06','09','11')
    and substr(lossdate,7,2) > '30'

根据您的输入界面，您可能需要重复31个月才能显示大于31的值。

select * 
from table 
where substr(lossdate,5,2) in ('01','03','07','08','10','12')  
    and substr(lossdate,7,2) > '31'

二月有点棘手。逐步开始，确定29天内的所有2月条目，您可以立即删除/修复这些条目。

select * 
from table 
where substr(lossdate,5,2) = '02' 
    and substr(lossdate,7,2) > '29'

然后，您需要对2月日期大于28且不是year年的其余行重复此操作。在过去的100年中，任何可被4整除的年份都是a年，因此您可以使用此标识剩余的年份（假设您更正/删除了已经找到的不良2月条目）：

select * 
from table 
where substr(lossdate,5,2) = '02' 
    and mod(substr(lossdate,1,4),4)) <> 0 
    and substr(lossdate,7,2) > '28'

SQL中的有效日期验证

2 个答案: