Case Statement

Hello,

Please assist with understanding this case statement. Let me know if any additional information is needed.
where
ca.addressid =
(
  case
    when (select count(*) from dss.contactaddress where contactid = ca.contactid and addresstype='Home' and program = ca.program) =0
      then (case
              when (select count(*) from dss.contactaddress where contactid = ca.contactid and preferred='1' and program = ca.program) =0
                then (select min(addressid) from dss.contactaddress where contactid = ca.contactid and program = ca.program)
                else (select min(addressid) from dss.contactaddress where contactid = ca.contactid and preferred='1' and program = ca.program)
            end)
      else (select min(addressid) from dss.contactaddress where contactid = ca.contactid and addresstype='Home' and program = ca.program)    
  end)
jverasqlAsked:
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sdstuberCommented:
If the  number of Home addresses is 0 and the number of addresses with Preferred = 1 is 0 then
return rows where the addressid is the MINIMUM address id for that contact and program

If the number of Home addresses is 0 and the number of addresses with preferred = 1 is NOT 0 then
return rows where the address is the MINIMUM address id where preferred = 1 for that contact and program

if the number of Home addresses is NOT 0 then
return rows where the address is the MINIMUM address id for Home addresses for that contact and program
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slightwv (䄆 Netminder) Commented:
The general syntax of the CASE statement you have is:
CASE
   WHEN "this"="this" THEN this
   WHEN "that"="that" THEN that
   ELSE something_else
END

If you break the giant case down and indent properly, you'll see you just have nested case statements.

What parts are confusing?
0
PortletPaulfreelancerCommented:
WHERE ca.addressid =
      (
      CASE
            WHEN (                                     -- CHECK for HOME ADDRESS
                  SELECT
                        COUNT(*)
                  FROM dss.contactaddress
                  WHERE contactid = ca.contactid
                        AND addresstype = 'Home'
                        AND program = ca.program
            )
            = 0 THEN (CASE                             -- if NO home address
                  WHEN (                                    -- CHECK for PREFERRED ADDRESS
                        SELECT
                              COUNT(*)
                        FROM dss.contactaddress
                        WHERE contactid = ca.contactid
                              AND preferred = '1'
                              AND program = ca.program
                  )                                         -- if no preferred address
                  = 0 THEN (                                -- USE first available ADDRESS
                        SELECT
                              MIN(addressid)
                        FROM dss.contactaddress
                        WHERE contactid = ca.contactid
                              AND program = ca.program
                  )                
                  ELSE (                                    -- use first preferred ADDRESS
                        SELECT
                              MIN(addressid)
                        FROM dss.contactaddress
                        WHERE contactid = ca.contactid
                              AND preferred = '1'
                              AND program = ca.program
                  ) END)
            ELSE (                                    -- There IS a home address so use it
                  SELECT
                        MIN(addressid)
                  FROM dss.contactaddress
                  WHERE contactid = ca.contactid
                        AND addresstype = 'Home'
                        AND program = ca.program
            ) END)

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sdstuberCommented:
jverasql - can I ask why a split didn't include the first post - did it not answer your question?  I does (I think) explain exactly what your nested case statements do.  If not, what's missing?
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