How Can I Efficiently Implement an Insert or Update Operation in SQL Server?

Optimizing "Insert or Update" Operations in SQL Server

SQL Server offers several efficient methods for performing "insert or update" operations, ensuring data integrity while maximizing performance. This involves updating an existing record if it exists, or inserting a new one if not.

One strategy leverages transactions to prevent deadlocks and primary key conflicts:

<code class="language-sql">BEGIN TRAN
IF EXISTS (SELECT * FROM table WITH (UPDLOCK, SERIALIZABLE) WHERE key = @key)
BEGIN
  UPDATE table SET ...
  WHERE key = @key
END
ELSE
BEGIN
  INSERT INTO table (key, ...)
  VALUES (@key, ...)
END
COMMIT TRAN</code>

Alternatively, a highly efficient approach uses the SERIALIZABLE isolation level:

<code class="language-sql">BEGIN TRAN
UPDATE table WITH (SERIALIZABLE) SET ...
WHERE key = @key

IF @@ROWCOUNT = 0
BEGIN
  INSERT INTO table (key, ...) VALUES (@key, ...)
END
COMMIT TRAN</code>

These techniques provide developers with robust and performant solutions for handling "insert or update" scenarios in SQL Server, guaranteeing data accuracy and operational efficiency.

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