postMay 12, 2026

SQL: SELECT and WHERE — your first query

#sql#basics#data-engineering

sql

SELECT
  user_id,
  email,
  created_at
FROM users
WHERE country = 'MX'
  AND created_at >= '2026-01-01';

SELECT picks which columns to return from a table. WHERE filters which rows to include. Together they form the most basic question you can ask a database: which records match my criteria, and what data do I want back?

In data engineering you write hundreds of these queries — exploring new data sources, validating pipeline outputs, debugging mismatched counts. Internalize the order: SELECT columns, FROM table, WHERE condition. The rest of SQL builds on this foundation.