Can we use delete with MERGE statement in Oracle?

Can we use delete with MERGE statement in Oracle?

2 Answers. No, you cannot delete rows that have not been updated by the merge command. Specify the DELETE where_clause to clean up data in a table while populating or updating it. The only rows affected by this clause are those rows in the destination table that are updated by the merge operation.

Can we use Delete in MERGE statement?

You can use the MERGE statement that specifies stock as the target table, manufact as the source table, a join condition in the ON clause, and with the Delete clause for the stock rows with incorrect manufacturer codes, as in the following example: MERGE INTO stock USING manufact ON stock.

How does MERGE work in Oracle?

Use the MERGE statement to select rows from one or more sources for update or insertion into a table or view. You can specify conditions to determine whether to update or insert into the target table or view. This statement is a convenient way to combine multiple operations.

Is MERGE faster than insert update?

The basic set-up data is as follows. We’ve purposely set up our source table so that the INSERTs it will do when merged with the target are interleaved with existing records for the first 500,000 rows. These indicate that MERGE took about 28% more CPU and 29% more elapsed time than the equivalent INSERT/UPDATE.

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.

Why MERGE is faster than UPDATE in Oracle?

The UPDATE statement will most likely be more efficient than a MERGE if the all you are doing is updating rows. Given the complex nature of the MERGE command’s match condition, it can result in more overhead to process the source and target rows.

Is commit required after MERGE?

If the merge succeeds without conflict, git will automatically commit it (which you should be able to verify by simply checking git log ).

Why MERGE is faster than update in Oracle?

How can you improve the performance of a MERGE statement in Oracle?

Adding a where-clause in the UPDATE-part to only update records when the values are actually different. If you are merging the same data over and over again and only a smaller subset of the data is actually modified, this will improve performance.

Is MERGE faster than delete and insert?

What is the difference between first merge and second merge in SQL?

First Merge uses a Static value (1) to perform the Join whereas Second Merge uses Column Alias to do the same. However, First Merge, expected to Update three rows and delete two of them (those having C3 > 1000) does not delete them but just updates them. Second Merge, deletes the data from Target table which does not happen in First scenario.

What is the delete clause in a merge?

The DELETE in a merge is not for non-existence. From the docs Specify the DELETE where_clause to clean up data in a table while populating or updating it. The only rows affected by this clause are those rows in the destination table that are updated by the merge operation.

What is merge_update_clause in Oracle?

The merge_update_clause specifies the new column values of the target table. Oracle performs this update if the condition of the ON clause is true. If the update clause is executed, then all update triggers defined on the target table are activated.

Can you delete rows that have not been updated by Merge?

I have tried this in oracle 10g and, with this sqlfiddle, oracle 11g. No, you cannot delete rows that have not been updated by the merge command. Specify the DELETE where_clause to clean up data in a table while populating or updating it.