# Set operators

[Read this page in HTML](https://www.scopedb.io/docs/reference/commands/query-operators/set)

Combine the rows returned by two queries.

## UNION ALL

`UNION ALL` combines two result sets and keeps duplicate rows. Columns are matched by position. Both sides must return the same number of columns with compatible types.

### Syntax

```scopeql
<query> UNION ALL <query>
```

### Examples

Combine checkout events from two sources. One source sends event IDs as strings and the other as integers; cast the integers to strings before combining them:

```scopeql
(
    VALUES ('17', 'payment_failed'), ('42', 'payment_completed')
    SELECT $0 AS event_id, $1 AS event
    UNION ALL (
        VALUES (63, 'payment_failed')
        SELECT $0::string AS event_id, $1 AS event
    )
)
ORDER BY event_id
```

```text
+----------+-------------------+
| event_id | event             |
+----------+-------------------+
| 17       | payment_failed    |
| 42       | payment_completed |
| 63       | payment_failed    |
+----------+-------------------+
```

Without the cast, the query fails because the first column is `string` on one side and `int` on the other.

Place `ORDER BY` or `LIMIT` after the closing parenthesis to apply it to the combined result.