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
Tag
beginner
54 posts
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
CSV
Querying a Folder of CSV Files With a Glob in DuckDB
Read every CSV in a folder as one table in DuckDB with a glob, add the file name as a column, and handle files whose columns differ in count or order.
8 min read
YAML
Using Anchors to Reduce Repetition in YAML Config Files
Put shared settings in one anchored block and merge it into each service. The web service replaced the whole environment block, since the merge is shallow.
6 min read
CSV
Letting DuckDB Sniff the Delimiter and Types of a CSV
How the DuckDB CSV sniffer picks delimiter, header and types, how to read its verdict with sniff_csv, and what breaks when a bad value sits past the sample.
9 min read
CSV
DuckDB read_csv Options You Will Actually Need in Practice
The read_csv options that solve real problems in DuckDB 2.0, each on a file that needs it, including the nullstr trap that replaces the empty default.
7 min read
CSV
How to Run SQL Directly on a CSV File With the DuckDB CLI
Install DuckDB, point it at a CSV and query it. Covers the file name shortcut, DESCRIBE, SUMMARIZE, reading from a pipe and writing CSV back out.
7 min read
Editor's pick
CSVGuide
Querying CSV Files With DuckDB Instead of Loading Them
DuckDB runs SQL on a CSV file with no import, no schema and no server. See what it guesses, what that costs, where it fails, and how to make it strict.
22 min read
YAML
Fixing Special Characters That Break YAML Values Safely
Colons, hashes, braces, backslashes and percent signs in YAML values: which break, which load silently wrong, tested outputs and the quoting rule.
6 min read