---
title: "Merge Support Functions"
id: functions-merge-support
pg_version: "20devel"
---

<a id="functions-merge-support"></a>

## 9.24. Merge Support Functions

PostgreSQL includes one merge support function that may be used in the `RETURNING` list of a [MERGE](sql-merge.md) command to identify the action taken for each row; see [Table 9.69](functions-merge-support.md#functions-merge-support-table). 

<a id="functions-merge-support-table"></a>

**Merge Support Functions**

| Function | Description | 
| --- | --- |
| `merge_action` ( ) → text | Returns the merge action command executed for the current row. This will be `'INSERT'`, `'UPDATE'`, or `'DELETE'`. |  |

Example: 
MERGE INTO products p
  USING stock s ON p.product_id = s.product_id
  WHEN MATCHED AND s.quantity > 0 THEN
    UPDATE SET in_stock = true, quantity = s.quantity
  WHEN MATCHED THEN
    UPDATE SET in_stock = false, quantity = 0
  WHEN NOT MATCHED THEN
    INSERT (product_id, in_stock, quantity)
      VALUES (s.product_id, true, s.quantity)
  RETURNING merge_action(), p.*;

 merge_action | product_id | in_stock | quantity
--------------+------------+----------+----------
 UPDATE       |       1001 | t        |       50
 UPDATE       |       1002 | f        |        0
 INSERT       |       1003 | t        |       10
 

Note that this function can only be used in the `RETURNING` list of a `MERGE` command. It is an error to use it in any other part of a query.