Record should only be loaded to target on a scenario - sql

Question

I have two tables a stage table and a target table. I want my target table to hold valid CustomerScore values. Currently, we insert into staging and load to our target table. We do not want to load invalid values(-8.0000). However, if there is a customerNumber with a valid value in our target table we would like to decommission numbers by giving it a customerScore of (-8.0000). This should be the only time this value makes it into the target table, so a record for that CustomerNumber has to already be in the target for this to update that record currently in the target table. My create statement is below
CREATE TABLE stg.CustomerAppreciation (
CustomerId INT identity(1, 1)
,CustomerNumber VARCHAR(50)
,CustomerScore DECIMAL(5, 4)
);
CREATE TABLE ods.CustomerAppreciation (
CustomerId INT identity(1, 1)
,CustomerNumber VARCHAR(50)
,CustomerScore DECIMAL(5, 4)
);
Currently, my target table has two records, each value below belongs to my create table fields.
1 123 0.8468
2 143 1.0342
Now say we want to decommission CustomerID = 2 because there is a record been inserted into staging as
3 143 -8.0000
The target table should now be updated on this CustomerNumber. Making my target table look like:
1 123 0.8468
2 143 -8.0000
This should be the only time we allow -8.0000 into the table when a CustomerNumber already exists. If a customerNumber does not exists in the target table and for some reason -8.0000 is seen in staging it should not be allowed in. How would I write an update query that updates a record in my target table only if that scenario exists and prevents -8.0000 from coming in if it does not exist?

Answer 1

Assuming the staging table only contains one row per customer number (if not, group it to show the highest customer Id), you can use a merge to perform this function. Without checking exact syntax, something like this:
MERGE ods.CustomerAppreciation AS Target
USING (SELECT * FROM stg.CustomerAppreciation WHERE CustomerScore >= 0) AS Source ON Target.CustomerNumber = Source.CustomerNumber
WHEN MATCHED
-- choose your match criteria here
--AND Source.CustomerId > Target.CustomerId
AND NOT EXISTS (SELECT Target.* INTERSECT SELECT Source.*)
THEN UPDATE
SET Target.CustomerScore = Source.CustomerScore;

Answer 2

Not sure if I fully understand the specifics but here is some syntax that should help to at least get you started ...
BEGIN;
MERGE ods.CustomerAppreciation AS X
USING (SELECT CustomerNumber,CustomerScore FROM stg.CustomerAppreciation) AS Y (CustomerNumber,CustomerScore)
ON (X.CustomerNumber = Y.CustomerNumber)
WHEN MATCHED /*AND Y.CustomerNumber = '-8.0000'*/ THEN
UPDATE SET CustomerScore = Y.CustomerScore
WHEN NOT MATCHED BY X /*AND Y.CustomerNumber = '-8.0000'*/ THEN
INSERT (CustomerNumber,CustomerScore)
VALUES (Y.CustomerNumber,Y.CustomerScore)
OUTPUT $action, inserted.* INTO #MyTempTable;
END;