Exam DP-420 topic 1 question 22 discussion

Actual exam question from Microsoft's DP-420

Question #: 22
Topic #: 1

HOTSPOT -
You have a container that stores data about families.
The following is a sample document.

You run the following query against the container.

For 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:

Show Suggested Answer

Suggested Answer:

Box 1: No -
The result is empty, since the cross product of each item from source and an empty set is empty:
Note: Joins result in a complete cross product of the sets participating in the join. The result of an N-way join is a set of N-element tuples, where each value in the tuple is associated with the aliased set participating in the join and can be accessed by referencing that alias in other clauses.

Box 2: No -
The cross join is not on the pets.

Box 3: Yes -
The cross join is not on the pets.
Reference:
https://docs.microsoft.com/en-us/azure/cosmos-db/sql/sql-query-join

by YJC at Nov. 3, 2022, 2:47 a.m.

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YJC

Highly Voted 2 years ago

After I tested with JSON, the answer is Yes, No, Yes

upvoted 29 times

ferpin

1 year, 7 months ago

You are right!

upvoted 1 times

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susejzepol

1 year, 11 months ago

You are right! In the first question the query return a value because "c" is represent the entire document and not only the parent's array.

upvoted 5 times

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4415b99

6 months, 4 weeks ago

it depends what is meant by `having a parent defined`. my understanding is that parent = document. so, it probably means that there is no document which corresponds to the format specified above and as a result those children have nowhere to exist. so, the answer is No, No, Yes. even if u put only { "children": [...] } as an item, it will mean that the parent is defined. while the parent's name, pets and other properties except children r not defined.

upvoted 1 times

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basiltomato

Highly Voted 1 year, 8 months ago

Also tested this. There's missing comma and should be ch.firstname instead of firstName: SELECT ch.name ?? ch.firstname AS childName, f.lastName, f.parents, ARRAY_LENGTH(ch.pets) ?? 0 AS numberOfPets, ch.pets FROM mktest1 AS f JOIN ch IN f.children Answer is YES, NO, YES