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Exam Certified Data Engineer Professional All Questions

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Exam Certified Data Engineer Professional topic 1 question 93 discussion

Actual exam question from Databricks's Certified Data Engineer Professional
Question #: 93
Topic #: 1
[All Certified Data Engineer Professional Questions]

You are performing a join operation to combine values from a static userLookup table with a streaming DataFrame streamingDF.

Which code block attempts to perform an invalid stream-static join?

  • A. userLookup.join(streamingDF, ["userid"], how="inner")
  • B. streamingDF.join(userLookup, ["user_id"], how="outer")
  • C. streamingDF.join(userLookup, ["user_id”], how="left")
  • D. streamingDF.join(userLookup, ["userid"], how="inner")
  • E. userLookup.join(streamingDF, ["user_id"], how="right")
Show Suggested Answer Hide Answer
Suggested Answer: B 🗳️
by Enduresoul at Nov. 26, 2023, 6:50 p.m.

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Enduresoul
Highly Voted 1 year ago
Selected Answer: B
Answer B is correct: https://spark.apache.org/docs/latest/structured-streaming-programming-guide.html#support-matrix-for-joins-in-streaming-queries When we take a look in the supported join matrix between static and stream inputs, we can identify, that Stream-Static + outer is not supported. Answer E is wrong, because the Static-Stream + right join is supported.
upvoted 10 times
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imatheushenrique
Most Recent 5 months, 4 weeks ago
B. We match all the records from a static DataFrame on the left with a stream DataFrame on the right. If records do not match from the static DF (Left) to stream DF (Right), then the system cannot return null since the data changes on stream DF (Right), and we cannot guarantee if we will get matching records. That is why full_outer join is not supported.
upvoted 2 times
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hal2401me
8 months, 2 weeks ago
Selected Answer: E
in my exam today, BCD are removed. i chose E, because I recall that stream-static right join are less supported.
upvoted 4 times
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Curious76
9 months ago
Selected Answer: B
b is correct
upvoted 1 times
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vctrhugo
9 months, 3 weeks ago
Selected Answer: B
Specifically, outer joins are not supported with a static DataFrame on the right and a streaming DataFrame on the left. This is because it’s not possible to guarantee all necessary rows will be available in the streaming DataFrame for every micro-batch.
upvoted 1 times
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kz_data
10 months, 2 weeks ago
Selected Answer: D
I think the correct answer is D.
upvoted 1 times
kz_data
10 months, 2 weeks ago
Sorry I missread the question.
upvoted 1 times
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lexaneon
10 months, 3 weeks ago
Selected Answer: B
believe B is correct as provided below
upvoted 2 times
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