Crystal/Oracle parameterized query to use variable

Question

I currently have a Database Command object in my Crystal Report that looks something like

SELECT *
    FROM table
    WHERE field = {?EndDate}

I want to change it so it looks more like

IF {?EndDate} = DATE '1900-01-01' 
    MyVariable = ADD_MONTHS(LAST_DAY(SYSDATE), -1)
ELSE
    MyVariable = {?EndDate}

SELECT * 
    FROM table
    WHERE field = MyVariable

I kind of get the idea of how to build a dynamic query to do this, but I don't know if that's really what I want to do. Could someone point me in the right direction, please? Thanks.

Answer 1

Select * 
from table
where field = decode
         (myvariable,'1900-01-01',ADD_MONTHS(LAST_DAY(SYSDATE), -1)
                    ,myvariable)

[Reads: select * from my table where field is equal to.. Decode myvariable; if it's 1-1-1900, then get a month before the current sysdate, otherwise, use the variable]

Something like that.