SQL Database Validation with AI: Check Data Like a Tester
Learn SQL database validation with AI. Find missing links, duplicates and bad values, write safe read-only queries and verify every result yourself.
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61 articles · page 1 of 6 · Clear filtersSQL Window Functions
Learn SQL window functions step by step: OVER(), PARTITION BY, ORDER BY in the window, aggregates without GROUP BY, named windows and frames, in MySQL 8.4.
MySQL Users and Roles
Manage MySQL accounts: CREATE USER, user@host, passwords, ALTER and DROP USER, roles with CREATE ROLE and default roles, and least-privilege account design.
SQL UNION and UNION ALL
Combine query results with SQL UNION and UNION ALL: rules for columns, removing duplicates, sorting the combined result, and when UNION ALL is faster.
SQL Subqueries
Learn SQL subqueries step by step: scalar and IN subqueries, derived tables in FROM, subqueries in SELECT, and when a JOIN or CTE is better.
SQL Top N per Group
Get the top N rows per group in SQL: top earners per department, best-selling products per category, latest order per customer, with ties handled correctly.
SQL Running Totals and Moving Averages
Calculate running totals, cumulative counts, moving averages and percent of total in SQL with SUM() OVER, window frames ROWS and RANGE, in MySQL 8.
SQL Project: QA Test Results Tracker
A SQL project for QA engineers: pass rates per build, failing and flaky tests, regressions with LAG, slowest tests, automation coverage and defect metrics.
SQL ROW_NUMBER, RANK and DENSE_RANK
The difference between ROW_NUMBER, RANK and DENSE_RANK explained on real data with ties, plus NTILE, ranking per group and the Nth highest salary, in MySQL.
SQL Recursive CTE
Learn recursive CTEs in MySQL 8: WITH RECURSIVE, anchor and recursive parts, number and date series, employee hierarchies, org-chart paths and loop limits.
SQL Project: Library Management System
Build and query a library management database in MySQL: available copies, overdue loans, fines, popular books, members, a view and an issue-book procedure.
SQL Project: Banking Transactions
A banking SQL project in MySQL: reconcile balances, running-balance statements, fraud patterns with window frames, an ACID transfer procedure and a trigger.
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