Beyond the Basics: Considerations for Effective UPSERT in SQL

MySQL:

MySQL doesn't have a dedicated UPSERT command, but you can achieve it using INSERT ... ON DUPLICATE KEY UPDATE:

INSERT INTO my_table (column1, column2, ...)
VALUES (value1, value2, ...)
ON DUPLICATE KEY UPDATE
  column1 = VALUES(column1),
  column2 = VALUES(column2),
  ...;

This statement attempts to insert a new row. If a row with the same value in the primary key already exists, it updates the specified columns with the new values.

Oracle:

Oracle provides a dedicated MERGE statement for UPSERT operations:

MERGE INTO my_table t
USING (
  SELECT value1, value2, ... FROM source_data
) s
ON (t.id = s.id) -- Match on the id column
WHEN MATCHED THEN
  UPDATE SET t.column1 = s.column1,
             t.column2 = s.column2,
             ...
WHEN NOT MATCHED THEN
  INSERT (column1, column2, ...)
  VALUES (s.value1, s.value2, ...);

This statement first attempts to match rows in the my_table with rows in the provided source_data based on the id column. If a match is found (MATCHED clause), it updates the corresponding columns in my_table. If no match is found (NOT MATCHED clause), it inserts a new row with the provided data.

PostgreSQL:

PostgreSQL offers the INSERT ... ON CONFLICT statement:

INSERT INTO my_table (column1, column2, ...)
VALUES (value1, value2, ...)
ON CONFLICT (id) -- Specify conflict target (e.g., primary key)
DO UPDATE SET
  column1 = EXCLUDED.column1,
  column2 = EXCLUDED.column2,
  ...;

Similar to the previous examples, this statement attempts to insert a new row. If a conflict occurs due to a duplicate value in the specified column (e.g., id), it updates the existing row with the new values from the excluded row (represented by EXCLUDED).

• Performance: Depending on the database and the size of the data, UPSERT operations might be less performant than separate INSERT and UPDATE statements. Consider performance implications when dealing with large datasets.
• Error handling: Ensure proper error handling in your code to gracefully handle scenarios where the UPSERT operation fails due to unexpected reasons.