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liandk

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.

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Latest from liandk

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liandk

Aug 20, 2026 · Databases

Master MySQL Locks: Row, Table, and Gap Lock Basics, Pitfalls & Live Code

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.

Gap LockLocksRow Lock

0 likes · 10 min read

Master MySQL Locks: Row, Table, and Gap Lock Basics, Pitfalls & Live Code

liandk

Aug 20, 2026 · Databases

Mastering SQL Subqueries: Core Nested Query Techniques for Beginners

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.

Database TutorialJOIN vs SubqueryNested Query

0 likes · 6 min read

Mastering SQL Subqueries: Core Nested Query Techniques for Beginners

liandk

Aug 19, 2026 · Databases

Mastering Multi-Table JOINs: Core Techniques for Real-World Data Relationships

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.

INNER JOINJOINLEFT JOIN

0 likes · 3 min read

Mastering Multi-Table JOINs: Core Techniques for Real-World Data Relationships

liandk

Aug 17, 2026 · Databases

MySQL Transaction Basics: ACID, Isolation Levels, and Practical Pitfall‑Avoiding Code

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.

ACIDIsolation LevelSQL

0 likes · 10 min read

MySQL Transaction Basics: ACID, Isolation Levels, and Practical Pitfall‑Avoiding Code

liandk

Aug 16, 2026 · Databases

Understanding DELETE vs DROP: How to Remove Data Without Dropping the Table

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.

DELETEDROP TABLEData manipulation

0 likes · 2 min read

Understanding DELETE vs DROP: How to Remove Data Without Dropping the Table

liandk

Aug 14, 2026 · Databases

Hands‑On MySQL Slow Query: Enable Logs, Analyze SQL, and Optimize Performance

The article explains what MySQL slow queries are, why they must be detected, when to enable slow‑query logging, step‑by‑step commands to configure the log, how to simulate and analyze problematic SQL with EXPLAIN, and practical optimization techniques—including index creation and Spring Boot integration—to eliminate performance bottlenecks.

SQLSlow QuerySpring Boot

0 likes · 10 min read

Hands‑On MySQL Slow Query: Enable Logs, Analyze SQL, and Optimize Performance

liandk

Aug 14, 2026 · Databases

Safe SQL UPDATE Practices: Changing Phone Numbers, Statuses, and Prices Without Risk

This article explains how the SQL UPDATE statement modifies existing rows, emphasizes the necessity of a WHERE clause to avoid full‑table changes, provides single‑row, batch, and multi‑column examples, and advises verifying data with SELECT before executing updates in production.

Data ModificationSQLSQL tips

0 likes · 2 min read

Safe SQL UPDATE Practices: Changing Phone Numbers, Statuses, and Prices Without Risk

liandk

Aug 13, 2026 · Databases

How to Use ORDER BY to Automatically Sort SQL Query Results

When query results appear unordered, the SQL ORDER BY clause lets you instantly arrange rows by ascending or descending values—such as timestamps, amounts, or multiple fields—providing clean, organized output for latest‑first displays, statistical sorting, and tidy list presentations.

ORDER BYSQLdatabase

0 likes · 2 min read

How to Use ORDER BY to Automatically Sort SQL Query Results

liandk

Aug 12, 2026 · Databases

MySQL Indexes from Scratch: What They Are, Why They Matter, and Hands‑On Performance Tests

This article explains MySQL indexes with a simple book‑catalog analogy, shows why missing or mis‑used indexes cause severe latency and CPU issues, outlines when to create or avoid indexes, and provides a step‑by‑step SpringBoot demo that measures query time dropping from 80‑200 ms to under 5 ms.

B+TreeEXPLAINIndex

0 likes · 10 min read

MySQL Indexes from Scratch: What They Are, Why They Matter, and Hands‑On Performance Tests

liandk

Aug 11, 2026 · Databases

Mastering SELECT: The Most Used SQL Query for Beginners

SELECT is the most frequently used SQL command, handling about 80% of data‑related work; this guide explains its core role, basic operations such as selecting all rows, specific columns, distinct values, and row limits, shows practical code examples, and advises against using SELECT * for better performance.

Data RetrievalSQLSQL Basics

0 likes · 2 min read

Mastering SELECT: The Most Used SQL Query for Beginners