# first, first\_value

[Read this page in HTML](https://www.scopedb.io/docs/reference/functions/aggregate/first)

Returns the first value in a group. `first_value` skips NULL values.

## Syntax

```scopeql
first(<expr>)
first_value(<expr>)
```

## Arguments

| Argument | Type     | Description  |
| -------- | -------- | ------------ |
| `<expr>` | Any type | Input value. |

## Returns

Returns the same type as the input.

* `first` returns the first value, even if it is NULL.
* `first_value` returns the first non-NULL value, or NULL if all values are NULL.
* Both return NULL for empty input.

## Usage notes

Use `WITHIN GROUP ORDER BY` before `AGGREGATE` to define row order. Without an explicit order, the selected value can vary.

## Examples

Compare the first campaign value with the first non-NULL campaign in a session:

```scopeql
VALUES
    ('s-17', 1, NULL::string), ('s-17', 2, 'spring'),
    ('s-17', 3, 'loyalty'), ('s-17', 4, NULL)
SELECT $0 AS session_id, $1 AS sequence, $2 AS campaign
GROUP BY session_id
WITHIN GROUP ORDER BY sequence
AGGREGATE
    first(campaign) AS earliest_campaign,
    first_value(campaign) AS earliest_known_campaign
```

```text
+------------+-------------------+-------------------------+
| session_id | earliest_campaign | earliest_known_campaign |
+------------+-------------------+-------------------------+
| s-17       | NULL              | spring                  |
+------------+-------------------+-------------------------+
```

`first` preserves the missing value on the earliest event; `first_value` skips it.