DP-420 Exam - Question 50

Question

HOTSPOT -You have a database named telemetry in an Azure Cosmos DB Core (SQL) API account that stores IoT data. The database contains two containers named readings and devices. Documents in readings have the following structure. ✑ id✑ deviceid✑ timestamp✑ ownerid✑ measures (array)- type- value- metricidDocuments in devices have the following structure. ✑ id✑ deviceid✑ owner- ownerid- emailaddress- name✑ brand✑ modelFor each of the following statements, select Yes if the statement is true. Otherwise, select No. NOTE: Each correct selection is worth one point. Hot Area:.

Examice · Accepted Answer

Box 1: Yes -Need to join readings and devices. Box 2: No -Only readings is required. All required fields are in readings. Box 3: No -Only devices is required. All required fields are in devices.

jdsherrington · Answer

Answer is NYN.

1. N: The readings container does not need to be read to return all deviceids associated with a particular emailaddress, so only one query is needed:
SELECT *
FROM devices d
WHERE d.owner.emailaddress = ________

2. Y: measures is an array, and to filter or project fields from an array, you need to use join to create a cross join with the array.
SELECT r.deviceid, r.ownerid, r.timestamp, m.value
FROM readings r
JOIN m IN r.measures
WHERE m.metricid = ________

3. N: owner is an object, not an array, so you can directly access the properties. deviceid, ownerid, emailaddress and model all exist in the devices container, so the readings container is not needed.
SELECT d.deviceid, d.owner.ownerid, d.owner.emailaddress, d.model
FROM devices d

grada · Answer

Who ever wrote the suggested responses has no idea of what a JOIN does in a document database... it has nothing to do with joining documents, but is an inner-document join.

It's NYN if the first questions means returning only devices, and none of the readings. It's YYN otherwise, because readings are in a separate container, and should be fetched using a second query.

Internal_Koala · Answer

No. Yes. Yes.

====================
First: No

SELECT *
FROM d
WHERE d.emailaddress =

"To return (?) for all devices ...". Sounds like the word "metrics" might be missing. If so, the answer is Yes and a second query must be added.
===========
SELECT d.deviceid
FROM d
WHERE d.emailaddress = ?

SELECT *
FROM m
WHERE m.deviceid = @deviceid

====================
Second: Yes

SELECT m.deviceid
FROM m
WHERE m.metricid = ?

SELECT d.deviceid, o.ownerid, d.timestamp
FROM d
JOIN o IN d.owner
WHERE d.deviceid = @deviceid

====================
Third: Yes

SELECT d.deviceid, o.ownerid, d.emailaddress, d.model
FROM d
JOIN o IN d.owner

kdsingh · Answer

The correct answer is YYN
- Yes: you need 2 requests, because the data is in 2 different containers.
- Yes: you need join to get the data from Array
- No: No joins required

avocacao · Answer

Y - requires 2 requests to get from 2 containers
Y - need join to get 'value' in measures array
Y - need join to get 'ownerid' and 'emailaddress' in owner array
https://learn.microsoft.com/en-us/azure/cosmos-db/nosql/query/join

Shiven · Answer

N - Device container has all required info. 
N - In Reading container we have everything. 
Y - Need to join 2 containers.

azuredemo2022three · Answer

Answer YYN

DP-420 Exam - Question 50

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