What are indexes in databases, why are they needed, and what is their internal structure?
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Tell about your recent work experience, what projects, what stack?
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228
What is the difference between UNION and UNION ALL? What conditions must be met?
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213
What groups of SQL operators do you know? What do they include?
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202
What is the Catalyst optimizer in Spark and what specific optimizations does it perform (e.g., predicate pushdown)?
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201
How does Hash Join work?
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200
What is normalization? Which form do we mainly work with?
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194
How do you verify data correctness when translating a pipeline from SAS to DBT?
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194
What causes deadlocks and which mechanism in databases is responsible for data consistency during parallel queries?.
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192
Why did you choose DBT? What are the pros and cons of this framework?
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191
Data Quality checks — at what stage, what checks, what happens to invalid data?
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189
Have you worked with data quality incidents?
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187
What are the features and differences of Set from List in Python? Besides performance, what other features are there?
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186
Tell about an interesting task in the last 2.5 years in the company, for example related to ClickHouse.
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186
How does Merge Join (sort-merge join) work?
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174
What formats of distribution are there in Greenplum besides BY column and RANDOMLY?
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171
Describe the sequence of operations in an SQL query with SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY, LIMIT from first to last.
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170
Do you prefer to work individually as an expert or in a team of developers?
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168
What types of physical table joins exist (Hash Join, Merge Join, Nested Loop)?
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167
If you join transactions with clients by client_id and date_start (without BETWEEN), what will be captured in the result?
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167