Microsoft SQL Server - best way to 'Update if exists, or Insert'

user_1959054 0
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I've been searching around for the answers to this question, and there's some conflicting or ambiguous information out there, finding it hard to find a for-sure answer.

My context: I'm in node.js using the 'mssql' npm package. My SQL server is Microsoft SQL Server 2014.

I have a record that may or may not exist in a table already -- if it exists I want to update it, otherwise I want to insert it. I'm not sure what the optimal SQL is, or if there's some kind of 'transaction' I should be running in mssql. I've found some options that seem good, but I'm not sure about any of them:

Option 1: how to update if exists or insert

Problem with this is I'm not even sure this is valid syntax in MSSQL. I do like it though, and it seems to support doing multiple rows at once too which I like.

INSERT INTO table (id, user, date, points)
    VALUES (1, 1, '2017-03-03', 25),
           (2, 1, '2017-03-04', 25),
           (3, 2, '2017-03-03', 100),
           (4, 2, '2017-03-04', 150)
    ON DUPLICATE KEY UPDATE points = VALUES(points)

Option 2:

don't know if there's any problem with this one, just not sure if it's optimal. Doesn't seem to support multiple simultaneous rows

update test set name='john' where id=3012
IF @@ROWCOUNT=0
   insert into test(name) values('john');

Option 3: Merge, https://dba.stackexchange.com/questions/89696/how-to-insert-or-update-using-single-query

Some people say this is a bit buggy or something? This also apparently supports multiple at once which I like.

MERGE dbo.Test WITH (SERIALIZABLE) AS T
USING (VALUES (3012, 'john')) AS U (id, name)
    ON U.id = T.id
WHEN MATCHED THEN 
    UPDATE SET T.name = U.name
WHEN NOT MATCHED THEN
    INSERT (id, name) 
    VALUES (U.id, U.name);
sql-server sql
3 Answers

Every one of them has different purpose, pros and cons.

Option 1 is good for multi row inserts/updates. However It only checks primary key constraints.

Option 2 is good for small sets of data. Single record insertion/update. It is more like script.

Option 3 is best for big queries. Lets say, reading from one table and inserting/updating to another accordingly. You can define which condition to be satisfied for insertion and/or update. You are not limited to primary key/unique constraint.

user_11189780

If your system is highly concurrent, and performance is important - you can try following pattern, if updates are more common than inserts:

BEGIN TRANSACTION;
 
UPDATE dbo.t WITH (UPDLOCK, SERIALIZABLE) SET val = @val WHERE [key] = @key;
 
IF @@ROWCOUNT = 0
BEGIN
  INSERT dbo.t([key], val) VALUES(@key, @val);
END
 
COMMIT TRANSACTION;

Reference: https://sqlperformance.com/2020/09/locking/upsert-anti-pattern

Also read: https://michaeljswart.com/2017/07/sql-server-upsert-patterns-and-antipatterns/

If inserts are more common:

BEGIN TRY     
  INSERT INTO dbo.AccountDetails (Email, Etc) VALUES (@Email, @Etc);       
END TRY     
BEGIN CATCH     
  -- ignore duplicate key errors, throw the rest.
  IF ERROR_NUMBER() IN (2601, 2627) 
    UPDATE dbo.AccountDetails
       SET Etc = @Etc
     WHERE Email = @Email;     
END CATCH

I wouldn't use merge, while most of the bugs are apparently fixed - we have had major issues with it before in production.

EDIT ---

Yes above answers were for single rows - For multiple rows, you'd do something like this: The idea behind the locking is the same though

BEGIN TRANSACTION;
 
  UPDATE t WITH (UPDLOCK, SERIALIZABLE) 
    SET val = tvp.val
  FROM dbo.t AS t
  INNER JOIN @tvp AS tvp
    ON t.[key] = tvp.[key];
 
  INSERT dbo.t([key], val)
    SELECT [key], val FROM @tvp AS tvp
    WHERE NOT EXISTS (SELECT 1 FROM dbo.t WHERE [key] = tvp.[key]);
 
COMMIT TRANSACTION;
user_21021320

Extending my comment here. There are known problems with MERGE in SQL Server, however, for what you're doing here you will likely be ok. Aaron Bertrand has an article on the subject which you can find here: Use Caution with SQL Server's MERGE Statement.

An alternative, however, for what you could do here would be using an "UPSERT"; UPDATE the existing rows, and then INSERT the ones that don't exist. This involves 2 separate statements, however, was the method used prior to MERGE:

UPDATE T
SET T.Name = U.Name
FROM dbo.Test T
     JOIN (VALUES (3012, 'john')) AS U (id, name) ON T.id = U.id;

INSERT INTO dbo.Test (Name) --I'm assuming ID is an `IDENTITY` here
SELECT U.name
FROM (VALUES (3012, 'john')) AS U (id, name)
WHERE NOT EXISTS (SELECT 1
                  FROM dbo.Test T
                  WHERE T.ID = U.ID);

Note I have not declared any locking or transactions in this example, but you should in any implemented solution.

user_20299830
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