Beginner~2h
String & Date Functions in SQL & DatabasesInterview Readiness Check
DATE_TRUNC, index-hostile function wrapping, STRING_AGG, TIMESTAMPTZ vs TIMESTAMP timezone bugs.
date_truncextractstring_aggconcattimezonetimestamptzinterval
Learning path
Try a sample question
SELECT DATE_TRUNC('month', '2024-03-15 14:30:00'::TIMESTAMPTZ) returns:
A.'2024-03-15 00:00:00' — truncates to the start of the day
B.'2024-03-31 00:00:00' — truncates to the last day of the month
C.'2024-03-01 00:00:00' — truncates to the first day of the month at midnight
D.'2024-01-01 00:00:00' — truncates to the first day of the year
Sign up free to take the full check and see the answer with an explanation.
What this module tests
- Conceptual understanding of string & date functions fundamentals
- Trade-offs and design decisions in real system scenarios
- date_trunc and extract — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
Take the String & Date Functions check →
10 questions · Dimension scoring · AI coach feedback · Shareable result
Test your knowledge — free →No credit card · Takes 10–15 min
Frequently asked questions
- What does the String & Date Functions check test?
- The check covers date_trunc, index-hostile function wrapping, string_agg, timestamptz vs timestamp timezone bugs. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for String & Date Functions?
- Key concepts include: date_trunc, extract, string_agg, concat, timezone, timestamptz, interval. These frequently appear in sql & databases interviews at product and infrastructure companies.
- How many questions are in the check?
- Each check has 10 questions — a mix of MCQ and short-answer. You get scored by dimension (e.g., scalability, consistency) so you know exactly where to focus.
- How long does it take to study String & Date Functions?
- Most engineers spend around 2 hours on this module. The check itself takes about 10–15 minutes. You can retake it up to 3 times per day.
- What prerequisite knowledge do I need before String & Date Functions?
- String & Date Functions builds on NULL Handling. Complete those first for the best results.
- Is date_trunc, extract, string_agg covered?
- Yes. The String & Date Functions module covers date_trunc, extract, string_agg among other key concepts. The check includes questions that reflect real sql & databases interview patterns.