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Questions tagged sql · hard

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What is the difference between SparkSession and SparkContext in Spark?

Spark/Big Datahardoptimizationpythonspark0.7 min read

AltimetrikAmerican ExpressCitiHexaware+3

What is a Common Table Expression (CTE), and when would you use it?

SQLhardbigqueryoptimizationsnowflake0.4 min read

AccentureCognizantEPAMYash Technologies

What is the difference between a primary key and a unique key?

SQLhardsparksql0.4 min read

AccentureCognizantEPAMYash Technologies

How does Spark's Catalyst Optimizer work? Explain its stages.

Spark/Big Datahardjoinoptimizationspark0.5 min read

DunnhumbyFragma Data SystemsHashedIn

How do you optimize Spark jobs for better performance? Mention at least 5 techniques.

Spark/Big Datahardjoinoptimizationpartition0.5 min read

Fragma Data SystemsPresidioSwiggy

What is Snowflake's architecture, and why is it unique?

Cloud/Toolshardbigqueryjoinoptimization3 min read

EYIncedoTech Mahindra

Retrieve the most recent sale_timestamp for each product (Latest Transaction).

General/Otherhardbigquerypartitionsnowflake0.6 min read

What is the difference between OLTP and OLAP?

General/Otherhardbigqueryetljoin0.7 min read

AareteDunnhumbyFragma Data Systems

How do you optimize a long-running SQL query?

SQLhardjoinoptimizationpartition0.6 min read

AareteDunnhumbyIncedo

10

Design an anti-skew strategy for a join on a high-cardinality key with a long-tail distribution (e.g., a few keys hold 80% of rows). Cover salting, split-skew, AQE, and cost/operational trade-offs.

Spark/Big Datahard

11

Walk through the three AQE features in Spark 3.x (coalesce, join switch, skew join)—how they operate at shuffle boundaries, which configs enable them, and what happens when AQE cannot help.

Spark/Big Datahard

12

How do you optimize Spark jobs for performance?

Spark/Big Datahard

13

Implement a Spark job to find the top 10 most frequent words in a large text file.

Spark/Big Datahard

14

What is Spark's Catalyst Optimizer? Explain its stages.

Spark/Big Datahard

15

Why is SparkSession used in Spark 2.0 and later versions?

Spark/Big Datahard

16

Tell me about yourself and your professional background.

Behavioralhard

17

Core services of AWS used in data engineering?

Cloud/Toolshard

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