Problems inserting new data into SQL Server table - sql

Question

I am trying to do an if else insert into one table from another (a table type).
I am having problems where basically the first time the script runs it adds all data into the table OK but then if something is added to the source data afterwards, it does not add the new record and I don't know why.
I can't include the exact code but it looks like this...
UPDATE CUSTOMER
Set Target.Desc = Source.Desc
From #source source
WHERE Target.AccountNumber = Source.AccountNumber
IF ##ROWCOUNT=0
INSERT INTO CUSTOMER(AccountNumber, Desc)
SELECT Source.AccountNumber, Source.Desc
FROM #Source Source
I have also tried a traditional if else insert but it had the same results.
Can you see anything wrong that might be stopping the newly added records from being inserted?

Answer 1

Your current code will only work correctly if #source contains either all existing or all new rows.
You can use MERGE when this is not the case
MERGE CUSTOMER AS target
USING #source AS source
ON ( target.AccountNumber = source.AccountNumber )
WHEN MATCHED THEN
UPDATE SET [Desc] = source.[Desc]
WHEN NOT MATCHED THEN
INSERT (AccountNumber, [Desc])
VALUES (AccountNumber, [Desc]);

Answer 2

How about doing this instead of using ##ROWCOUNT
-- update existing customers
UPDATE c
SET c.Desc = Source.Desc
FROM #source source
INNER JOIN CUSTOMER c ON c.AccountNumber = Source.AccountNumber
-- insert new customers
INSERT INTO CUSTOMER(AccountNumber, Desc)
SELECT Source.AccountNumber, Source.Desc
FROM #Source Source
LEFT JOIN CUSTOMER c ON Source.AccountNumber = c.AccountNumber
WHERE c.AccountNumber IS NULL

Answer 3

-- update all existing rows
update c set
c.Desc = s.Desc
from CUSTOMER c
join #source s on s.AccountNumber=c.AccountNumber
-- insert all missing rows
insert into CUSTOMER (AccountNumber, Desc)
select s.AccountNumber, s.Desc
from #Source s
where not exists(
select *
from CUSTOMER c
where c.AccountNumber=s.AccountNumber
)

Answer 4

The first time, there is no data in your target so ##rowcount is 0.
Next time, the update updates all data and ##rowcount is not 0 and you get no data inserted.
You should not use ##rowcount but do what Andrew suggest: do both UPDATE and INSERT
or MERGE (do both in one statement)

Answer 5

##ROWCOUNT value contains the count of affected rows. the insert statement works only if all the records are new. and it does not go for updation. if any of the record got updated, it would not go for insertion even the source contains new records
If your requirement is to update existing records and Insert New records from source , you can use the below code.
-- update existing Rows
UPDATE CUSTOMER
SET CUSTOMER.Desc = SOURCE.Desc
from #SOURCE Source
WHERE Source.AccountNumber=CUSTOMER.AccountNumber
-- Insert New Data
INSERT INTO CUSTOMER (AccountNumber, Desc)
SELECT s.AccountNumber, s.Desc
FROM #Source Source
WHERE not exists( SELECT 1
FROM CUSTOMER
WHERE CUSTOMER.AccountNumber=Source.AccountNumber)