包含 db2 中的 where 条件的 where 子句中的 case

Question

我有一个用例，我需要在 where 子句中编写一个包含 case 语句的查询，条件如下：我在 'SAMPLE_TABLE' 中有一列名为 'BIRTHDATE' 1) if only from date (which is a param ie, :from)给出，然后我需要从 SAMPLE_TABLE 中获取其 BIRTHDATE >= :from 2) 的记录，如果只给出了迄今为止（这是一个参数，即 :to），然后获取其 BIRTHDATE <= :to 3) 的记录，如果两者都有给出起始日期和终止日期，然后获取这些日期之间的记录。

下面是我试过的查询。 但无法得到解决方案。

SELECT BIRTHDATE FROM SAMPLE_TABLE
    WHERE
    (CASE
      WHEN (:from AND NOT :to)
      THEN BIRTHDATE >= :receivefrom
      WHEN (:to AND NOT :from)
      THEN BIRTHDATE <= :to
      WHEN (:to AND :from)
      THEN BIRTHDATE BETWEEN :from AND :to
     END)

请提供一个有效的查询。 提前致谢。

Answer 1

此代码可以，当不包含日期时将其留空。 这是在 SQL Server 中测试过的

declare @from date='1998-12-07'
declare @to date ='2000-12-07'

SELECT [Birthdate] --when only from is available
FROM SAMPLE_TABLE
where (case when (@to='' and  @from !='') then 1 else 0  end)=1
and BIRTHDATE >= @from

UNION

SELECT [Birthdate] --when only to is available
FROM SAMPLE_TABLE
where (case when (@to!='' and  @from ='') then 1 else 0  end)=1
and BIRTHDATE <= @to

UNION

SELECT [Birthdate] --when both from and to are avilable
FROM SAMPLE_TABLE
where (case when (@to!='' and  @from !='') then 1 else 0  end)=1
and BIRTHDATE between @from and @to

或者你可以试试这个

declare @from date='1998-12-07'
declare @to date ='2000-12-07'

IF (@from!='' and @to!='')

SELECT [Birthdate] 
FROM SAMPLE_TABLE
Where [Birthdate] between @from and @to 

ELSE IF (@from='' and @to!='')

(SELECT [Birthdate] 
FROM SAMPLE_TABLE
Where [Birthdate]<= @to)

ELSE IF (@from!='' and @to='')

(SELECT [Birthdate] 
FROM SAMPLE_TABLE
Where [Birthdate]>= @from)

Answer 2

我想你只是想要：

SELECT BIRTHDATE
FROM SAMPLE_TABLE
WHERE (BIRTHDATE >= :from OR :from IS NULL) AND
      (BIRTHDATE <= :to OR :to IS NULL)

Answer 3

我假设如果不应该传递某个参数，那么它具有 NULL 值。

where birthdate between coalesce(:from, date('0001-01-01')) and coalesce(:to, date('9999-12-31'))