Using CASE statement compare 3 conditions and have the statements executed

问题

I have a requirement where in i'm supposed to take 3 dynamic values from the user and compare with the list of values present based on match of it I need to have conditions to be added to where clause using case statement.

select *
from   MY_DBSOURCE
WHERE  1=1
And LP_WHERE_REP = (CASE When :LP = 'LIFESHEILD' AND     :M = 'AP' AND :STATUS = 'Processed' THEN flag ='P' and Manual_FLAG = 'P' END)
AND     DATA_SOURCE IN ('LIFESHIELD') 
AND     DATE_CLOSED >= '15-JUL-2019'
AND     DATE_CLOSED <= '16-JUL-2019'

回答1:

CASE can be used in WHERE, but - syntax should be OK. Yours isn't.

Here's an example which shows how to do it (also, note that I used date literal for date_closed; you compared it to strings.

select *
from   my_dbsource
where  1=1
and lp_where_rep = case when :lp = 'LIFESHEILD' and :m = 'AP' and :status = 'Processed' then 'P' 
                        when manual_flag = 'P' then 'X'
                        else 'Y'
                   end
and     data_source in ('LIFESHIELD') 
and     date_closed >= date '2019-07-15'
and     date_closed <= date '2019-07-16'

回答2:

If you want to use a case in WHERE clause then you can use something like the following:

AND (CASE WHEN :LP = 'LIFESHEILD' AND :M = 'AP' AND :STATUS = 'Processed' THEN flag ELSE 'P' END) = 'P'
AND (CASE WHEN :LP = 'LIFESHEILD' AND :M = 'AP' AND :STATUS = 'Processed' THEN Manual_FLAG ELSE 'P' END) = 'P'

Cheers!!

来源：https://stackoverflow.com/questions/57040183/using-case-statement-compare-3-conditions-and-have-the-statements-executed