This article explains why indexing long character columns can bloat MySQL indexes, introduces the concept of index selectivity, shows how to calculate the best prefix length with real‑world queries, and demonstrates performance differences between short and optimal index prefixes.
This article explains how to determine the optimal order of columns in MySQL composite indexes by analyzing B+Tree structure, index selectivity, and real‑world query performance, providing practical examples and SQL demonstrations to help developers create more efficient indexes.
This article explains the concept of MySQL index cardinality, how it influences index selectivity, factors that affect cardinality values, methods to view them, and demonstrates with practical examples how different data distributions and query patterns impact the optimizer's execution plans.
This article explains how Oracle's Cost‑Based Optimizer estimates the selectivity of range predicates without histograms, demonstrates calculations with sample data, shows PL/SQL code for converting string values to internal numbers, and discusses pitfalls such as identical internal values causing cardinality errors, offering solutions like gathering histograms or using DATE columns.
