CSV
Loading a CSV From a URL Into PostgreSQL Without Saving It
Stream a CSV from a web address straight into COPY with curl. See what a 404 and a cut off download do to a plain pipe, and the guards that fix it.
8 min read
Library
Everything you need to level up your coding skills.
XML
Converting XML to Excel With Python and Typed Cells
Write an XML file into an xlsx workbook with openpyxl so numbers are numbers, booleans are booleans and identifiers stay text, and read it back to check.
7 min read
Excel
VLOOKUP and XLOOKUP Versus SQL JOIN With Worked Examples
Translate VLOOKUP and XLOOKUP into SQL joins: exact and approximate match, first-match behavior, not-found values, duplicates and which side to keep.
7 min read
JSON
Extracting Nested JSONB Values With Path Operators
PostgreSQL reads deep JSONB values with #> and #>>, and filters with jsonpath. How array paths, missing keys, strict mode and wildcards actually behave.
8 min read
CSV
Loading a Gzipped CSV Into PostgreSQL Without Unpacking It
Stream a gzipped CSV into PostgreSQL with gunzip and COPY, time it against unpacking first, and see what a truncated archive does to a pipe.
8 min read
ExcelGuide
Translating Excel Formulas Into SQL With Worked Examples
Translate Excel formulas into SQL: lookups, conditional sums, IF, text and date functions, running totals and pivots, with a worked dataset and the traps.
18 min read
CSV
Skipping Bad Rows During a PostgreSQL CSV Import Safely
PostgreSQL 17 can skip rows with bad values during COPY. See ON_ERROR, REJECT_LIMIT and verbose logging in action, and the errors they do not cover.
7 min read
XML
Converting XML to CSV for Spreadsheet Users Safely
Turn a nested XML file into a flat CSV with Python, joining repeated authors into one cell with correct quoting, and see why pandas read_xml dropped one.
7 min read
YAML
YAML Duplicate Keys and the Silent Overwrite Problem
PyYAML keeps the last of a repeated key silently, ruamel.yaml raises and yamllint flags it. A strict loader in eight lines and how merges create duplicates.
6 min read
CSV
Handling NULL and Empty Strings in PostgreSQL CSV Imports
PostgreSQL loads an unquoted empty field as NULL and a quoted one as an empty string. See the options that change that and the integer error one causes.
8 min read
JSON
Querying JSONB With the Arrow Operators in PostgreSQL
How -> and ->> read keys and array elements in PostgreSQL JSONB, what comes back for missing keys, and the precedence and casting traps that bite.
8 min read
ExcelGuide
Reading and Writing Excel Files With openpyxl in Python
A working guide to openpyxl: the workbook model, reading values and formulas, writing and editing files, large-file modes, styles, charts and errors.
19 min read
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