Oracle SQL Merge Statement with Conditions - sql

Question

I"m relatively new to SQL, and I'm having an issue where the target table is not being updated.
I have duplicate account # (key) with different contact information in the associated columns. I’m attempting to consolidate the contact information (source) into a single row / account number with the non duplicate contact information going into (target) extended columns.
I constructed a Merge statement with a case condition to check if the data exists in the target table. If the data is not in the target table then add the information in the extended columns. The issue is that the target table doesn’t get updated. Both Source and Target tables are similarity defined.
**Merge SQL- reduced query**
MERGE INTO target tgt
USING (select accountno, cell, site, contact, email1 from (select w.accountno, w.cell, w.site, w.contact, email1, row_number() over (PARTITION BY w.accountno order by accountno desc) acct
from source w) inn where inn.acct =1) src
ON (tgt.accountno = src.accountno)
WHEN MATCHED
THEN
UPDATE SET
tgt.phone4 =
CASE WHEN src.cell <> tgt.cell
THEN src.cell
END,
tgt.phone5 =
CASE WHEN src.site <> tgt.site
THEN src.site
END
I have validated that there is contact information in the source table for an accountno that should be added to the target table. I greatly appreciate any insight as to why the target table is not being updated.
I saw a similar question on Stack, but it didn't have a response.

Answer 1

Your SRC subquery in using clause, returns just 1 random row for each accountno.
You need to aggregate them, for example using PIVOT:
with source(accountno, cell, site, contact) as ( --test data:
select 1,8881234567,8881235678,8881236789 from dual union all
select 1,8881234567,8881235678,8881236789 from dual
)
select accountno, contact,
r1_cell, r1_site,
r2_cell, r2_site
from (select s.*,row_number()over(partition by accountno order by cell) rn
from source s
)
pivot (
max(cell) cell,max(site) site
FOR rn
IN (1 R1,2 R2)
)
So finally you can compare r1_cell, r1_site, r2_cell, r2_site with destination values and use required ones:
MERGE INTO target tgt
USING (
select accountno, contact,
r1_cell, r1_site,
r2_cell, r2_site
from (select s.*,row_number()over(partition by accountno order by cell) rn
from source s
)
pivot (
max(cell) cell,max(site) site
FOR rn
IN (1 R1,2 R2)
)
) src
ON (tgt.accountno = src.accountno)
WHEN MATCHED
THEN
UPDATE SET
tgt.phone4 =
CASE
WHEN src.r1_cell <> tgt.cell
THEN src.r1_cell
ELSE src.r2_cell
END,
tgt.phone5 =
CASE WHEN src.r1_site <> tgt.site
THEN src.r1_site
ELSE src.r2_site
END
/

Answer 2

the issue is with regards to the logic you have used in row_numbering the rows with identical account_number.
MERGE
INTO target tgt
USING (select accountno, cell, site, contact, email1
from (select w.accountno, w.cell, w.site, w.contact, email1
, row_number() over (PARTITION BY w.accountno order by w.accountno desc) acct
from source w
left join target w2
on w.accountno=w2.accountno
where w2.cell is null /* get records which are not in target*/
) inn
where inn.acct =1
) src
ON (tgt.accountno = src.accountno)
WHEN MATCHED THEN
UPDATE
SET tgt.phone4 = src.cell,
tgt.phone5 = src.site