Files & formats
Compare Two Parquet Files with DuckDB: Added, Deleted, and Changed Rows
Find added, deleted, and changed records across two Parquet exports.
DuckDB · Parquet
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Start tutorialThe Query.Farm workshop
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Find a hidden change. Untangle a messy match. Follow a slow query. Short DuckDB tutorials with data you can explore and SQL you can run.
Find your next experimentData included · Runs in your browser · Under 10 min read
Same row count. Same data?
Ada and Ben changed. Cy left; Eli joined.
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23 tutorials
Clean & match data
Fuzzy Matching in DuckDB: Match and Review Customer Names
Build a customer matching queue that flags ties, weak matches, and missing candidates.
DuckDB · RapidFuzz
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Performance & operations
Slow DuckDB Query? Check Where the Aggregate Runs
Find where an aggregate runs and use that boundary to investigate a slow query.
DuckDB · PostgreSQL · ADBC
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Files & formats
Read Nested JSON in DuckDB: Turn Orders into Rows
Flatten an order document without losing the orders whose item arrays are empty.
DuckDB · JSON
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SQL fundamentals
Why Your SQL JOIN Doubled the Total—and How to Fix It
Recognize row multiplication and produce a total that counts each order once.
DuckDB
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Clean & match data
Keep the Latest Row per Customer in DuckDB
Choose one deterministic latest record per key, then filter its current state.
DuckDB
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Clean & match data
Clean a Messy CSV in DuckDB and Account for Every Row
Produce clean invoice values and a review table that accounts for every input record.
DuckDB · CSV
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Clean & match data
Validate Incoming JSON with DuckDB and JSON Schema
Check a JSON contract and separate valid incoming records from records that need review.
DuckDB · JSON · JSON Schema
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Analyze data
Count Weekly Unique Visitors: Why Daily Counts Don’t Add Up
Combine daily visitor summaries into a period estimate while understanding overlap and approximation.
DuckDB · DataSketches
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SQL fundamentals
DuckDB ASOF JOIN: Find the Price at the Time of an Order
Match each event to the nearest earlier state for the same key, including events with no prior state.
DuckDB
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Performance & operations
Use parquet_metadata() to Understand Parquet Filter Performance
Read row-group statistics and explain which groups a date filter could rule out.
DuckDB · Parquet
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Performance & operations
Read a DuckDB EXPLAIN Plan: Follow the Rows Before You Run
Trace a query from its scan through aggregation to ordering, and distinguish estimates from measured rows.
DuckDB
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Performance & operations
DuckDB EXPLAIN ANALYZE: Measure the Rows Behind a Slow Query
Find unexpected row growth in a measured plan and verify a corrected query on the same data.
DuckDB
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Analyze data
Turn Clickstream Events into Sessions with DuckDB
Assign sessions with an explicit inactivity rule, then measure observed duration and engagement.
DuckDB
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Analyze data
Build a Conversion Funnel That Respects Event Order
Count sessions that viewed, ran an example, and enquired in order within a declared conversion window.
DuckDB
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Analyze data
Why Your Seven-Day Moving Average Isn’t Seven Days
Choose a calendar-aware moving average and make the missing-data assumption explicit.
DuckDB
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Files & formats
Combine CSV and Parquet Files When Columns Change
Read files with an added optional column while preserving provenance and diagnosing incompatible values.
DuckDB · CSV · Parquet
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SQL fundamentals
PIVOT and UNPIVOT in DuckDB: From Spreadsheet to Analysis
Convert month columns to long-form rows and rebuild a report without confusing unknown values with zeros.
DuckDB · CSV
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Analyze data
Build a Retention Cohort Table in DuckDB
Measure weekly return activity by signup cohort while preserving unknown future periods.
DuckDB
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Analyze data
Calculate Overall p95 Latency Without Averaging Percentiles
Calculate overall latency percentiles from observations or mergeable distributions instead of averaging percentile values.
DuckDB · DataSketches
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Files & formats
Reshape API Responses with JSONata in DuckDB
Construct a new JSON contract with renamed fields, calculated totals, and consistent array shapes.
DuckDB · JSON · JSONata
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Analyze data
Assign Users to Repeatable Experiment Groups with DuckDB
Map stable user IDs to repeatable buckets and distinguish a rollout threshold from a hash contract.
DuckDB · Hashfuncs
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SQL fundamentals
Find Missing Records with ANTI JOIN—and Avoid the NULL Trap
Audit unmatched records with existence semantics and explain how NULL changes a NOT IN predicate.
DuckDB
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