Can my DB?

MERGE INTO inventory AS t
USING daily_deltas AS s ON t.product_id = s.product_id
WHEN MATCHED AND s.delta < 0 THEN
  DELETE
WHEN MATCHED THEN
  UPDATE SET quantity = t.quantity + s.delta
WHEN NOT MATCHED THEN
  INSERT (product_id, quantity) VALUES (s.product_id, s.delta);

• Added in PostgreSQL 15.
• Supports multiple WHEN MATCHED clauses with conditions.
• WHEN NOT MATCHED BY SOURCE clause (for target rows with no match) added in PostgreSQL 17.

• MySQL does not support the MERGE statement.
• Use INSERT ... ON DUPLICATE KEY UPDATE for simple upserts.
• For more complex scenarios use a DELETE + INSERT pattern within a transaction.

• MariaDB does not support the MERGE statement.
• Use INSERT ... ON DUPLICATE KEY UPDATE or INSERT OR REPLACE for upsert patterns.

MERGE INTO inventory t
USING daily_deltas s ON (t.product_id = s.product_id)
WHEN MATCHED THEN UPDATE SET t.quantity = t.quantity + s.delta
WHEN NOT MATCHED THEN INSERT (product_id, quantity) VALUES (s.product_id, s.delta);

• Available since Oracle 9i.
• Supports WHEN MATCHED, WHEN NOT MATCHED, conditional UPDATE/DELETE, and a DELETE sub-clause within WHEN MATCHED.
• Error logging can be added via LOG ERRORS clause.

MERGE INTO inventory AS t
USING daily_deltas AS s ON t.product_id = s.product_id
WHEN MATCHED THEN UPDATE SET t.quantity = t.quantity + s.delta
WHEN NOT MATCHED BY TARGET THEN INSERT (product_id, quantity) VALUES (s.product_id, s.delta)
WHEN NOT MATCHED BY SOURCE THEN DELETE;

• Available since SQL Server 2008.
• Statement must end with a semicolon.
• Supports OUTPUT clause for RETURNING-like behavior.
• Supports WHEN NOT MATCHED BY SOURCE for rows present in the target but not the source.
• Has had concurrency bugs in older versions; apply current patches.

• SQLite does not support the MERGE statement.
• Use INSERT ... ON CONFLICT for upsert behavior.

MERGE INTO inventory
USING daily_deltas ON inventory.product_id = daily_deltas.product_id
WHEN MATCHED THEN UPDATE SET quantity = inventory.quantity + daily_deltas.delta
WHEN NOT MATCHED THEN INSERT (product_id, quantity) VALUES (daily_deltas.product_id, daily_deltas.delta);

• MERGE added to Redshift in 2023.
• Supports WHEN MATCHED THEN UPDATE/DELETE and WHEN NOT MATCHED THEN INSERT.
• Source can be a table, subquery, or VALUES list.

MERGE INTO inventory AS t
USING daily_deltas AS s ON t.product_id = s.product_id
WHEN MATCHED THEN UPDATE SET t.quantity = t.quantity + s.delta
WHEN NOT MATCHED THEN INSERT (product_id, quantity) VALUES (s.product_id, s.delta);

• Full SQL-standard MERGE support.
• Supports multiple WHEN MATCHED clauses with conditions.
• Supports SIGNAL to raise errors from within a MERGE action.

MERGE INTO inventory AS t
USING daily_deltas AS s ON t.product_id = s.product_id
WHEN MATCHED THEN UPDATE SET t.quantity = t.quantity + s.delta
WHEN NOT MATCHED THEN INSERT (product_id, quantity) VALUES (s.product_id, s.delta);

• Full MERGE support.
• Supports multiple WHEN MATCHED clauses with conditions.
• Also supports DML error handling via error tables.

MERGE INTO inventory AS t
USING daily_deltas AS s ON t.product_id = s.product_id
WHEN MATCHED THEN UPDATE SET t.quantity = t.quantity + s.delta
WHEN NOT MATCHED THEN INSERT (product_id, quantity) VALUES (s.product_id, s.delta);

• Full MERGE support.
• Source and target must be different tables.
• Supports WHEN NOT MATCHED BY SOURCE for target-only rows.
• MERGE is atomic within a transaction.