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first()
The first aggregate allows you to get the value of one column
as ordered by another. For example, first(temperature, time) returns the
earliest temperature value based on time within an aggregate group.
Required arguments
| Name | Type | Description |
|---|---|---|
value | TEXT | The value to return |
time | TIMESTAMP or INTEGER | The timestamp to use for comparison |
Sample usage
Get the earliest temperature by device_id:
SELECT device_id, first(temp, time)
FROM metrics
GROUP BY device_id;warning
The last and first commands do not use indexes, and instead perform a sequential scan through their groups. They are primarily used for ordered selection within a GROUP BY aggregate, and not as an alternative to an ORDER BY time DESC LIMIT 1 clause to find the latest value (which uses indexes).
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