Databricks Certified Data Engineer Professional — Question 168

A data engineer is 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?

Answer options

• A. userLookup.join(streamingDF, ["user_id"], how="right")
• B. streamingDF.join(userLookup, ["user_id"], how="inner")
• C. userLookup.join(streamingDF, ["user_id"), how="inner")
• D. userLookup.join(streamingDF, ["user_id"], how="left")

Correct answer: D

Explanation

The correct answer is D because performing a left join with a streaming DataFrame is not valid in this context. Options A and B are valid joins, and C contains a syntax error with a mismatched bracket. Therefore, D is the only option that indicates an invalid operation.