根据特定条件从SQL表中删除行

Question

I have a table that contains the following fields: issues to go (itg), customer number (ctm_nbr) and pub code (pub_cde). The data looks like this

12   010000024412  CTR
 6   010000024412  RTF
18   010000002325  CTR
 9   010000002325  RTF
 3   010000014789  CTR
 1   010000014789  RTF

I need to be able to delete all of the records where the RTF pub code and matching customer number is half of the issues to go (itg) in the CTR pub code for that matching customer. That way once I have all the records removed I would only have records like this remaining:

  3   010000014789  CTR
  1   010000014789  RTF

Answer 1

You might use something like: Delete all records for customer number x where the customer number has issues to go in CTR field that are twice the issues to go in the RTF field.

  Delete
    from --table--
   where ctm_nbr in (select t2.ctm_nbr
                       from --table-- t2 join --table-- t3 
                             ON (t2.ctm_nbr = t3.ctm_nbr)
                      where t2.pub_cde="CTR"
                        and t3.pub_cde="RTF"
                        and t2.itg = 2*t3.itg
                    )

Answer 2

You can use conditional aggregation:

delete from tbl
where ctm_nbr in(
select   ctm_nbr
from     tbl
group by ctm_nbr
having   max(case when pub_cde = 'CTR' then cast(itg as decimal) end) /
         max(case when pub_cde = 'RTF' then cast(itg as decimal) end) = 2)

Fiddle: http://sqlfiddle.com/#!6/a7efe/1/0

The reason I casted itg as decimal is to avoid the rounding issue that would otherwise occur due to your column being an interger data type (thanks to Laurence for pointing that out).

Answer 3

The tricky bit is getting both related records at one time:

delete
  a1
from
  a a1
where (
    a1.pub_cde = 'RTF' and 
    exists (
      select 'x'
      from   a a2
      where  a2.ctm_nbr = a1.ctm_nbr and
             a2.pub_cde = 'CTR' and
             a2.itg = 2 * a1.itg
    )
  ) or (
    a1.pub_cde = 'CTR' and
    exists (
      select 'x'
      from   a a2
      where  a2.ctm_nbr = a1.ctm_nbr and
             a2.pub_cde = 'RTF' and
             a2.itg * 2 = a1.itg 
    )
  );

Example SQL Fiddle

Answer 4

DELETE t1
FROM a t1
INNER JOIN a t2
  ON t1.ctm_nbr = t2.ctm_nbr
WHERE 
  ((t1.pub_cde = 'CTR') AND 
  (t2.pub_cde = 'RTF') AND 
  (2*t2.itg = t1.itg))
OR
  ((t2.pub_cde = 'CTR') AND 
  (t1.pub_cde = 'RTF') AND 
  (2*t1.itg = t2.itg))