When not matched by source does it DELETE?

We can use WHEN NOT MATCHED BY SOURCE clause in SQL Server MERGE statement to delete the rows in the target table that does not match join condition with a source table. For example, the row with locationID =2 in the target table does not match the join condition and the row is present only in the target table.

Can we use DELETE in MERGE statement?

The MERGE statement basically works as separate INSERT, UPDATE, and DELETE statements all within the same statement. You specify a “Source” record set and a “Target” table and the JOIN condition between the two.

Can we use DELETE in MERGE statement in Oracle?

DELETE Clause An optional DELETE WHERE clause can be added to the MATCHED clause to clean up after a merge operation. Only those rows in the destination table that match both the ON clause and the DELETE WHERE are deleted.

Does MERGE DELETE rows?

A single MERGE statement can also combine both DELETE and INSERT operations, or can combine both UPDATE and INSERT operations without deleting any rows. The source table is unchanged by the MERGE statement.

When not matched clause in MERGE statement?

The MERGE statement can have only one WHEN NOT MATCHED [ BY TARGET ] clause. Specifies that all rows of *target_table, which don’t match the rows returned by ON , and that satisfy any additional search condition, are updated or deleted according to the clause.

Why are my MERGE statements not performing as well?

Therefore, MERGE statements that contain literal values may not perform as well as individual INSERT, UPDATE, or DELETE statements because a new plan is compiled each time the MERGE statement is executed. To improve query performance, we recommend the following parameterization guidelines:

What does merge_not_matched mean in SQL?

WHEN NOT MATCHED [ BY TARGET ] THEN . Specifies that a row is inserted into target_table for every row returned by ON that doesn’t match a row in target_table, but satisfies an additional search condition, if present.

What happens when you merge in SQL Server?

For every insert, update, or delete action specified in the MERGE statement, SQL Server fires any corresponding AFTER triggers defined on the target table, but doesn’t guarantee on which action to fire triggers first or last. Triggers defined for the same action honor the order you specify.