Editor's pick
CSVGuide
Handling CSV Files Too Big to Open in Excel or Python
A decision guide for CSV files too big to open: look, count, sample, query in place, chunk, split, compress or convert, with numbers from a 1.3 GB file.
17 min read
Topic
DuckDB
Analytics with no server in sight. Point SQL at CSV, Parquet and JSON files and get answers in seconds.
CSV
Converting a CSV to Parquet and Why You Might Want To
One DuckDB statement turned a 130 MB CSV into a 34 MB Parquet file; typed columns, dictionary encoding and min/max statistics explain the faster queries.
10 min read
XML
Using DuckDB to Read XML Through Python and Arrow Tables
Stream XML into Arrow batches with lxml, query them in DuckDB at once, or try the community webbed extension. 1.2 million lines in 7.9 s with a 53 ms query.
6 min read
CSV
Calculating Month Over Month Growth From a CSV in SQL
Compute month over month growth with lag(): revenue of 46.50, 202.00 and 382.00 grew 334.4% and then 89.1%. Partial months, gaps and a zero base need care.
6 min read
CSV
Filling Gaps in a CSV Time Series With SQL and DuckDB
Find and fill missing days in a CSV time series: build a calendar with range(), left join the data and choose zero, carry-forward or interpolation.
7 min read
CSV
Joining Two CSV Files on a Messy Key Without Losing Rows
Join two CSVs on a messy key: a strict join matched 1 of 4 orders, a normalized key matched 3, and an anti-join listed the rest. Check counts and duplicates.
6 min read
CSV
Writing Query Results Back Out to CSV With DuckDB COPY
Export a DuckDB query to CSV with COPY. Control the delimiter, NULL text, quoting, date format and compression, and split output into one file per value.
9 min read
CSV
Joining Two CSV Files With SQL in DuckDB Without a Database
Join two CSV files on a key with plain SQL in DuckDB. Covers a 2M by 250k row join, keys that differ by case and spaces, left and anti joins, and type errors.
8 min read
CSV
Converting a CSV to Parquet With DuckDB in One Line
One COPY statement turns a CSV into Parquet in DuckDB. See the schema it writes, fix zip and money columns, compare compression codecs, and verify the result.
8 min read
CSV
DuckDB Skipping Bad Rows While Reading a Messy CSV
Use ignore_errors and store_rejects in DuckDB to read past bad CSV rows, then query reject_errors to see which lines were dropped and why.
9 min read
CSV
Reading a CSV With Mixed Date Formats in DuckDB Safely
A date column with five formats makes DuckDB fall back to text. Parse it with try_strptime and coalesce, list the failures, and avoid the day-first trap.
7 min read
CSV
Fixing DuckDB CSV Type Detection That Guessed Wrong
When the DuckDB CSV sniffer picks the wrong type, override it by column, read as text and cast, or narrow the candidate types. A test file shows each guess.
8 min read
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