DRTauli DRTauli - 7 months ago 48
SQL Question

Oracle Merge vs Select then Insert or Update

What is faster?

the Merge statement

MERGE INTO table_name
USING dual
ON (row_id = 'some_id')
WHEN MATCHED THEN
UPDATE SET col_name = 'some_val'
WHEN NOT MATCHED THEN
INSERT (row_id, col_name)
VALUES ('some_id', 'some_val')


or

querying a select statement then using an update or insert statement.

SELECT * FROM table_name where row_id = 'some_id'


if rowCount == 0

INSERT INTO table_name (row_id,col_name) VALUES ('some_id','some_val')


else

UPDATE table_name SET col_name='some_val' WHERE row_id='some_id'

Answer

The rule of thumb is, if you can do it in one SQL, it'll generally perform better than doing it in multiple SQL statements.

I'd go with the MERGE if it does the job.

Also - another suggestion: you can avoid repeating data in your statement, e.g.:

MERGE INTO table
 USING (SELECT 'some_id' AS newid,
               'some_val' AS newval
        FROM dual)
 ON (rowid = newid)
WHEN MATCHED THEN
 UPDATE SET colname = newval
WHEN NOT MATCHED THEN
 INSERT (rowid, colname)
 VALUES (newid, newval)