This article demonstrates how to create a score table in MySQL, insert sample data, and implement ranking of students using both user‑defined variables for pre‑8.0 versions and modern window functions like RANK(), DENSE_RANK() and ROW_NUMBER() to handle ties and gaps.
This article demonstrates how to calculate a running total for each code and date in a MySQL table by using user-defined variables, addresses the need to reset totals per code, and shows an optimized version with the WITH clause and indexing recommendations.
The article explains MySQL 8.0.22's new optimizer_switch variable derived_condition_pushdown, shows how enabling it can cause unexpected results with user‑defined variables in outer WHERE clauses, provides test cases, explains the underlying behavior, and offers three practical solutions.
This article explains how to calculate cumulative daily user totals in MySQL using user-defined variables, demonstrates the necessary SQL queries, compares them with a Java‑style algorithm, and highlights important considerations such as variable initialization and practical pitfalls.
This article demonstrates three distinct techniques—flooding undo logs, exhausting memory with user variables, and triggering a known bug—to deliberately crash a MySQL instance, explains the underlying mechanisms, shows test results, and offers practical safeguards to keep production databases stable.
