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toc_priority: 141
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# deltaSumTimestamp {#agg_functions-deltasumtimestamp}

Adds the difference between consecutive rows. If the difference is negative, it is ignored.

This function is primarily for [materialized views](../../../sql-reference/statements/create/view.md#materialized) that are ordered by some time bucket-aligned timestamp, for example, a `toStartOfMinute` bucket. Because the rows in such a materialized view will all have the same timestamp, it is impossible for them to be merged in the "right" order. This function keeps track of the `timestamp` of the values it's seen, so it's possible to order the states correctly during merging.

To calculate the delta sum across an ordered collection you can simply use the [deltaSum](../../../sql-reference/aggregate-functions/reference/deltasum.md#agg_functions-deltasum) function.

**Syntax**

``` sql
deltaSumTimestamp(value, timestamp)
```

**Arguments**

-   `value` — Input values, must be some [Integer](../../data-types/int-uint.md) type or [Float](../../data-types/float.md) type or a [Date](../../data-types/date.md) or [DateTime](../../data-types/datetime.md).
-   `timestamp` — The parameter for order values, must be some [Integer](../../data-types/int-uint.md) type or [Float](../../data-types/float.md) type or a [Date](../../data-types/date.md) or [DateTime](../../data-types/datetime.md).

**Returned value**

-   Accumulated differences between consecutive values, ordered by the `timestamp` parameter.

Type: [Integer](../../data-types/int-uint.md) or [Float](../../data-types/float.md) or [Date](../../data-types/date.md) or [DateTime](../../data-types/datetime.md).

**Example**

Query:

```sql
SELECT deltaSumTimestamp(value, timestamp)
FROM (SELECT number AS timestamp, [0, 4, 8, 3, 0, 0, 0, 1, 3, 5][number] AS value FROM numbers(1, 10));
```

Result:

``` text
┌─deltaSumTimestamp(value, timestamp)─┐
│                                  13 │
└─────────────────────────────────────┘
```