# SimpleAggregateFunction

`SimpleAggregateFunction` stores an aggregate's scalar partial result. The value can be read directly and combined with the ordinary aggregate again, without an intermediate-state merge or finalization call.

This works for sum, minimum and maximum: summing partial sums, for example, gives the sum of all original rows. An average needs both a total and a count, so use [AggregateFunction](https://coordinatordb.com/docs/reference/data-types/aggregatefunction) for it.

## Syntax

```text
SimpleAggregateFunction(function, T)
```

* `function` — `sum`, `min` or `max`.
* `T` — The scalar value type. Assigned values must satisfy this inner type's constraints.

Construct values with `sum_simple_state`, `min_simple_state` or `max_simple_state`, or write plain scalar values to the declared column.

## Example

### Reading and combining partial totals

```sql
CREATE TABLE partial_totals
(
    batch UInt8,
    total SimpleAggregateFunction(sum, UInt64)
);
INSERT INTO partial_totals VALUES (1, 30), (2, 90);
```

The values can be selected directly:

```sql
SELECT batch, total
FROM partial_totals
ORDER BY batch
FORMAT csv;
```

```text
1,30
2,90
```

Combine them with ordinary `sum`:

```sql
SELECT sum(total)
FROM partial_totals
FORMAT csv;
```

```text
120
```

Inserting rows does not automatically merge rows that have the same batch. Use an explicit aggregate query when you need a combined result.

See [aggregate combinators](https://coordinatordb.com/docs/reference/functions/aggregate-functions/combinators#_simple_state) for the `_simple_state` constructors.