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Your First SELECT -- Reading the Source of Truth
1.1Why Query the Database Directly?Every application has layers. A user clicks a button in the UI, which sends an HTTP request to the API, which executes business logic…1.2The Basic SELECT StatementThe SELECT statement retrieves data from one or more tables. It is the most fundamental SQL command and the one you will use most often as…1.3Verification Queries -- The QA Engineer's Bread and ButterAfter performing an action through the UI or API, verify the result at the database level. The database is the source of truth -- if the UI…1.4Why DB Verification Matters1.5Verify Record ExistenceThe simplest verification: does this record exist?1.6Verify Default ValuesWhen your application creates a record without specifying every field, the database should fill in sensible defaults.1.7Verify TimestampsTimestamps are a frequent source of bugs: wrong timezone, not updating on modification, impossible dates.1.8Find Data AnomaliesThese queries hunt for data integrity issues that indicate bugs in your application.1.9Connecting from Python -- Your First Automated DB TestConnecting to the database from your test code lets you verify persistence directly:1.10Using DictCursor for Readable AssertionsPositional access (row[0], row[1]) is fragile and hard to read. Use DictCursor instead:1.11Parameterized Queries (Prevent SQL Injection)Always use parameterized queries in test code:1.12Practice Schema 1: User Management1.13ExercisesBeginner:1.14Q&AResume phrasing- Authored SQL-based verification queries to validate data persistence across UI, API, and database layers, reducing production data bugs…1.15Q&ACover letter framingMy approach to quality starts at the source of truth: the database. I have built automated verification suites that go beyond UI and API…1.16Q&AInterview framing"I approach data verification by never trusting the UI or API response alone. After any state-changing operation, I write a SELECT query…1.17Q&AWhat not to say- "I just check the API response to verify data was saved." -- This shows you trust intermediary layers blindly and miss entire categories…1.18Q&AQuestion 1Prompt: You run an API test that creates a new user and the response is HTTP 201 with a valid JSON body. A week later, a customer reports…1.19Q&AQuestion 2Prompt: Your team's test suite uses SELECT * throughout all database verification queries. A new migration adds a JSONB column to the users…1.20Q&AQuestion 3Prompt: You need to verify that a soft-delete feature works correctly. The API returns 204 on DELETE, and the user no longer appears in the…