SUBSTRING()

Concepts covered: sqlSubstring

Basic Extraction Consider product codes that embed category information in specific positions. Extract to String End Practical Applications Parsing Email Domains This query finds the position of the @ symbol, adds 1 to skip past it, then extracts everything from that point to the end. The domain portion has variable length, so omitting the length parameter is essential. Fixed-Width Extraction Many legacy systems use fixed-width formats where each field occupies specific character positions: Best Practices When to Use SUBSTRING() This function is a workhorse in real-world data pipelines. SQL positions start at 1, not 0, so if you are used to zero-indexed programming languages, remember to shift your position arguments by 1 to avoid off-by-one extraction errors.

About This Interactive Section

This section is part of the String Functions: Intermediate 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.

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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.