Seasoned Java and mobile developer with years of experience, specializing in mini‑programs, public accounts, and full‑stack front‑end development. In the AI era, I continuously learn to broaden my knowledge and evolve. I revived a public account I started a decade ago during a dessert‑startup venture, using code as a vessel and knowledge as a companion. I share personal projects, technical articles, programming tips, and growth insights—let’s improve together and set sail.
This article explains how database views act as virtual tables that store only query logic, allowing developers to replace repetitive, multi‑join SQL statements with a single, reusable query while improving consistency, hiding sensitive fields, and boosting development efficiency.
The article explains why MySQL back‑table lookups (回表) double I/O and degrade performance, defines covering indexes that retrieve all needed columns from a secondary index, shows how to identify back‑table cases via EXPLAIN, and provides step‑by‑step commands to create, test, and verify covering indexes for high‑frequency queries.
The article explains how database transactions ensure atomicity, consistency, isolation, and durability, showing why they are essential for preventing data inconsistency, loss, and reconciliation errors, and provides step‑by‑step SQL examples of successful and rolled‑back transactions along with practical tips for safe usage.
This article explains MySQL InnoDB's MVCC mechanism, detailing how snapshot reads and current reads work, the hidden fields that drive versioning, the Read View rules for RC and RR isolation levels, and provides hands‑on SQL demos plus common pitfalls to avoid.
The article explains that indexes are the key to solving most database slow‑query problems, compares full‑table scans with indexed lookups, describes the two main index types in SQL Server, and provides step‑by‑step T‑SQL commands for creating, testing, and removing indexes while warning against over‑indexing.
Understanding MySQL’s lock types—table, row, and gap locks—reveals how they act as resource tokens to ensure data consistency under concurrency, while the article details their characteristics, appropriate and prohibited use cases, common pitfalls like lock degradation and deadlocks, and provides hands‑on SQL examples to reproduce and avoid these issues.
This guide explains why subqueries are essential after learning JOINs, outlines their core characteristics, common use cases, two main types, step‑by‑step examples—including single‑row, multi‑row, aggregate, and derived‑table queries—and lists five key rules to avoid pitfalls while showing when to prefer subqueries over JOINs.
This article explains the four fundamental SQL JOIN types, shows when to use each in real business scenarios, and provides a step‑by‑step example that creates tables, inserts data, and demonstrates LEFT and INNER JOIN queries with practical tips for readability.
The article explains what a database transaction is, breaks down the ACID properties, details MySQL’s four isolation levels with their appropriate use‑cases and pitfalls, and provides step‑by‑step SQL and SpringBoot code to reproduce and resolve dirty reads, non‑repeatable reads, and phantom reads.
This article clarifies the difference between SQL DELETE and DROP TABLE, showing that DELETE removes rows while preserving table structure (and requires a WHERE clause), whereas DROP TABLE eliminates the entire table, and provides practical scenarios and code examples for each.
