SQL Coding Question Count | Dataford Interview Questions

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Problem

Bosch Building Technologies uses binary sensor readings from building automation systems to monitor equipment states. Write a PostgreSQL query that counts how often readings with values 0 and 1 occur for each building with at least one active device.

Requirements

Join active devices to their sensor readings.
Count readings equal to 0 and readings equal to 1 separately for each building.
Include active buildings whose devices have no readings, returning zero counts where appropriate.
Ignore NULL readings and values other than 0 or 1, and sort the results alphabetically by building name.

Schema

devices

Column	Type	Description
device_idPK	INTEGER	Unique device identifier
device_name	VARCHAR(100)	Bosch Building Technologies device name
building_name	VARCHAR(100)	Building where the device is installed
sensor_type	VARCHAR(50)	Type of monitored sensor
is_active	BOOLEAN	Whether the device is currently active

sensor_readings

Column	Type	Description
reading_idPK	INTEGER	Unique reading identifier
device_id	INTEGER	Device that produced the reading
reading_value	SMALLINT	Binary or other recorded sensor value