channels

One row for each combination of channel and tags in a dataset, with its data type. Query this before reading points to learn what a dataset contains and which points_* table to read it from.

Telemetry table, so every query must filter by dataset_rid.

For what a channel is, see Channels in the data model.

Columns

Column	Type	Nullable	Notes
dataset_rid	VARCHAR	No	Dataset the channel belongs to. Required in the WHERE clause.
channel	VARCHAR	No	Channel name.
tags	MAP	No	Key-value pairs recorded with the series. See Filtering by tag.
data_type	VARCHAR	No	The channel’s value type, which tells you which table holds its data. See Data types.

Data types

data_type	Table holding the data
DOUBLE	points_double
INT64	points_int
STRING	points_string
STRUCT	points_struct
LOG	logs

Note

The SQL interface does not return units. Channels carry unit metadata in Nominal, but the SQL interface returns raw numbers. See 🔒︎Assign and convert units.

Examples

List everything in a dataset:

SELECT channel, data_type
FROM channels
WHERE dataset_rid = '<dataset-rid>'
ORDER BY channel

Group by type to see the shape of the dataset:

SELECT data_type, COUNT(*) AS channels
FROM channels
WHERE dataset_rid = '<dataset-rid>'
GROUP BY data_type
ORDER BY channels DESC

Filter by tag:

SELECT channel, data_type
FROM channels
WHERE dataset_rid = '<dataset-rid>'
  AND tags['<tag key>'] = '<tag value>'
ORDER BY channel

Next steps

• points_double: read the samples once you know the channel.

• datasets: dataset-level metadata and bounds.