case inside where clause which contains where conditions in db2

Question

I have use case where I need to write a query which contains case statement in where clause with conditions like below : I have column in 'SAMPLE_TABLE' called 'BIRTHDATE' 1) if only from date (which is a param ie, :from) is given, then I need to get the records from SAMPLE_TABLE whose BIRTHDATE >= :from 2) if only to date (which is a param ie, :to) is given,then get records whose BIRTHDATE <= :to 3) if both from and to dates are given, then get the records between those dates.

Below is the query I tried. But couldn't get the solution.

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)

Please provide a working query. Thanks in advance.

Answer 1

This code would do, when a date is not included leave it as blank. This was tested in SQL Server

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

Or else you can try this

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

I think you simply want:

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'))