sql merge output

Recently I’ve been making a lot of use of the OUTPUT option for insert and update actions.

Alternatively, there are different ways to sync the source and target table. OUTPUT clause in the merge statement will return one row for each row that is modified in the target table.

When all observations in the BY group have been read from one data set and there are still more observations in another data set, SAS performs a one-to-many merge until all observations …

We explored different aspects of SQL Server Merge Statement with several examples in this article. For example, the row with LocationID = 4 in the table Locations_stage does not match join condition and is present in the source table only. This happens when a target row matches more than one source row. WHEN NOT MATCHED BY TARGET clause is used to insert rows into target table that does not match join condition with a source table. Please refer to the below image for the output of the above script which shows action and the inserted and deleted data in SQL Server MERGE statement.

Rows with LocationID 1 and 3 are matched in the target and source table as per the join condition and the value of LocationName in the target was updated with the value of LocationName in the source table for both rows. If WHEN NOT MATCHED BY SOURCE clause in SQL Server MERGE statement was specified two times, one must use an update operation and another one must use delete operation. Now when we use WHEN NOT MATCHED BY TARGET clause in the merge statement to insert the additional row from Locations_stage into Locations. Because of this, OUTPUT behaves slightly differently. |   SQL Server DBA, Developer with good experience in SQL Server administration, development, performance tuning, monitoring, high availability and disaster recovery technologies It even supports with a MERGE statement, which was introduced in SQL Server 2008 version. Use inner join to update rows that match the join condition. Merge XML data into templates far simpler and easier than XSLT in 2 lines of code. The statement joins the target to the source by using a column common to both tables. You can use the OUTPUT clause to log any changes. 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. We can use additional search condition to filter the rows inserted into the target table. Following T-SQL script is the example of the OUTPUT clause in the MERGE statement. We can see that the merge statement did not update the row with LocationID 1 as it did not satisfy the additional search condition specified along with the WHEN MATCHED clause. SQL> The output shows the straight MERGE statement is an order of magnitude faster than its nearest rival. We cannot use WHEN NOT MATCHED BY SOURCE clause more than two times. In this case, the rows which do not match with join condition but satisfy the additional search condition were only inserted into the target table. Because of this, a variable called ‘$Action’ is utilised (only available in MERGE) which will show whether the output action was taken as a result of insert, update or delete.First of all, create a table with data to use for the merge:The result of this is two additional rows in the history table, one from the Inserted data and the other from the Deleted data. But we must write three different statements for synchronizing the tables. The update/insert performs almost twice the speed of the insert/update and even out performs the row-by-row MERGE.

Please refer to below T-SQL script for the example for the MERGE statement with two WHEN MATCHED clauses. If we are creating instead of triggers on the target table, we must create instead of triggers for all the DML actions specified in the MERGE statement. In this case, Locations is the target table, Locations_stage is the source table and the column LocationID is used in the join condition.

When there is more than one row in the source table that matches the join condition, the update in SQL Server MERGE statement fails and returns error “The MERGE statement attempted to UPDATE or DELETE the same row more than once. Please refer to the below example for the trigger on the target table and output clause in the MERGE statement.

The OUTPUT appears only once, at the end of the MERGE statement. MERGE statement is used to synchronize two tables by inserting, deleting, and updating the target table rows based on the join condition with the source table. If we create only INSTEAD OF INSERT trigger on the target table and specify INSERT, DELETE AND UPDATE operation in the MERGE statement, it throws an error.

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