sqlsybasesap-iq

Obtaining a field associated with the previous month in Sybase


In the query below, I am trying to get the BALANCE value from table loans for the same Uniq_ID and same year, but previous month, and then compare it to the current rows BALANCE value. The fdate column looks like 3/1/2019. I try to do it as below but get the error "Sybase Database Error: Feature, reference containing a scalar value subquery (defined at line 13) inside a conditional expression (CASE, COALESCE, ARGN, NULLIF, or IF), is not supported". How can I try to do this another way?

SELECT h.UNIQUEID, f.num
(select BALANCE from loans b
    where b.UNIQ_ID = h.UNIQ_ID
    and year(b.FDATE) = year(h.FDATE) 
    and MONTH(b.fdate) = MONTH(h.fdate) - 1) AS prev_bal,
(case when prev_bal > 0 and prev_bal >= BALANCE then 1 else 0 end) as  flag
FROM loans h, perform f
where f.uniq_id = h.uniq_id 

Edit:

The data looks like this:

fdate           UNIQUEID              NUM    BALANCE   
3/1/2019       LNSAR17224-00453434    1      16254.1  
4/1/2019       LNSAR17224-00453434    1      15643.2    

I would like to add the column prev_bal which looks as follows:

fdate           UNIQUEID              NUM    BALANCE   prev_bal    
3/1/2019       LNSAR17224-00453434    1      16254.1    {null}     
4/1/2019       LNSAR17224-00453434    1      15643.2    16254.1 

Expected Output:

UNIQUEID              NUM   prev_bal    flag
LNSAR17224-00453434    1    {null}       0
LNSAR17224-00453434    1    16254.1      1

Solution

  • Assumptions:

    One query that (I believe) addresses the above:

    select h.UNIQUEID,
           f.num,
           d1.prev_balance,
           isnull(d1.flag,0) as flag
    
    from   loans h
    join   perform f
    on     f.uniq_id = h.uniq_id
    
    left
    join   (select h2.UNIQ_ID,                                       -- data associated with previous date
                   h2.BALANCE as prev_balance,
                   case when h2.BALANCE > 0 and h2.BALANCE >= h.BALANCE 
                        then 1 
                        else 0
                   end as flag
            from   loans h2
            where  h2.UNIQ_ID = h.UNIQ_ID
            and    h2.FDATE = (select max(h3.FDATE) as prev_fdate    -- find previous date
                               from   loans h3
                               where  h3.UNIQ_ID = h2.UNIQ_ID
                               and    h3.FDATE   < h2.FDATE)
           ) as d1
    
    on     h.uniq_id = d1.uniq_id
    

    Or getting rid of one level of sub-queries:

    select h.UNIQUEID,
           f.num,
           h2.BALANCE as prev_balance,
           isnull(case when h2.BALANCE > 0 and h2.BALANCE >= h.BALANCE
                       then 1
                       else 0 
                  end,0) as flag
    
    from   loans h
    join   perform f
    on     h.uniq_id = f.uniq_id
    
    left
    join   loans h2
    on     h.uniq_id = h2.uniq_id
    and    h2.FDATE = (select max(h3.FDATE) as prev_fdate   -- find previous date
                       from   loans h3
                       where  h3.UNIQ_ID = h2.UNIQ_ID
                       and    h3.FDATE   < h2.FDATE)
    

    NOTE: Don't have table DDL, or sample data, so currently unable to test the above for syntax/data accuracy ...