String Types & Platform Traps

String types seem simple, but they differ across platforms in ways that cause real production issues. VARCHAR length limits, CHAR padding behavior, and TEXT vs VARCHAR semantics vary between PostgreSQL, MySQL, Snowflake, and BigQuery. Code that works on one platform can silently truncate data on another. Platform Differences That Bite UTF-8 and Character vs Byte Length VARCHAR(100) means 100 characters in PostgreSQL but 100 bytes in some MySQL configurations. A single emoji or CJK character can be 3-4 bytes in UTF-8. A VARCHAR(100) column in byte-mode MySQL can only hold 25 four-byte characters. Always confirm whether your database measures string length in characters or bytes.

About This Interactive Section

This section is part of the Schema Types lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live PostgreSQL database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

How DataDriven Lessons Work

DataDriven combines four interview rounds (SQL, Python, Data Modeling, Pipeline Architecture) with adaptive difficulty and spaced repetition. Easy problems get harder as you improve. Weak concepts resurface until you master them. Your readiness score tracks progress across every topic interviewers test. Every lesson section ends with problems you solve by writing and running real code, not by picking multiple-choice answers.