Provyn Prep · Data Analyst competency
Querying & joins in the Data Analyst assessment
Querying & joins is one of the areas a Provyn Data Analyst credential scores separately, so a recruiter can see it on its own rather than averaged into one number. This guide explains what it covers, how it is tested and what to practice.
What it covers
Pulling the right rows for an analysis: joins, filters, window functions and time-series queries.
Topics in the practice set for this area
- window functions
- time series
How it is tested
In the timed assessment, questions in this area use these formats: code you write, multiple choice, short answer. Each attempt draws its own set of questions, and this area gets its own sub-score on the credential when the attempt includes enough questions from it. The assessment questions themselves are never published; the practice set below is written separately for study.
What to practice
- Write a query that compares each day's value with the previous day's.
- Join an events table to a users table and check whether the row count changed unexpectedly.
- Bucket timestamps by week and month and handle days with no data.
Try a practice question
From the free practice set (5 questions in this area). Answers and explanations are in the practice set.
- A daily sales chart built from `GROUP BY sale_date` has no point at all for days with zero sales, so the line skips straight over them. What is the standard fix?
- Scores ordered from highest are 100, 90, 90, 80. What does DENSE_RANK() OVER (ORDER BY score DESC) give the score of 80?
- In Postgres, `DATE_TRUNC('week', TIMESTAMP '2025-06-18 15:00')` (a Wednesday) returns which value?
Practice before the real thing
Both are free and use practice questions only, never questions from the real assessment.
More Data Analyst study guides
Last reviewed 2026-10-06.