Is the MERGE Pattern the Most Efficient Way to Combine Inserts and Updates in SQL Server Stored Procedures?

Understanding the Merge Pattern in Stored Procedures for Efficient Inserts and Updates

In SQL Server, combining inserts and updates into a stored procedure presents a design challenge. One common approach involves attempting an update and performing an insert if the update affects no rows. While this pattern is perceived as efficient, it raises the question of whether it is the optimal solution.

The MERGE Pattern: The Optimal Approach

The correct way to combine inserts and updates is through the MERGE pattern. This pattern uses the UPDATE and INSERT statements in the same procedure, ensuring that:

• If the record exists, the UPDATE statement executes, effectively performing an implicit select.
• If the record does not exist, the INSERT statement executes, creating a new row.

Why It's Efficient

This approach is efficient because it eliminates the need for an explicit select to check for the existence of a record before performing an update. This saves one select statement when compared to alternatives that require both an explicit and implicit select. As explained by the resource from SQLServerCentral.com, every update eliminates an additional read from the table, reducing I/O operations.

Cautions

While the merge pattern is generally effective, it's important to note some potential issues:

• Race conditions can occur if there are multiple concurrent updates.
• Triggers may not fire correctly if both inserts and updates are performed in the same stored procedure.

To address these concerns, the linked blog post provides further insights and safe implementation techniques.

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