How to overwrite a record with same primary key in SQL Server?

Question

I am using Python to push data to SQL Server. Suppose I have a table like below:

I am pushing the data using following code and query

query = """INSERT INTO TestTable (Key, One, Two) values(?,?,?)"""

Next, I want to push a Data with values 'A2', 'A3' in column 'Two' and two new rows like below:

I want to have a query with inserts new row if the primary key is not present and overwrite the row when the primary key is present. I tried using REPLACE INTO instead of INSERT INTO but that does not seem to work in SQL Server.

Please can you help.

Answer 1

Sql Server supports the MERGE statement for upserts.

And to upsert 1 tupple, VALUES can be used.

MERGE TestTable AS t
USING (VALUES (?,?,?)) AS s([Key], One, Two) 
ON (s.[Key] = t.[Key])
WHEN NOT MATCHED BY Target THEN
  INSERT ([Key], One, Two) 
  VALUES (s.[Key], s.One, s.Two) 
WHEN MATCHED THEN UPDATE SET
  One = s.One,
  Two = s.Two;

db<>fiddle here