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Java Tech Enthusiast
Java Tech Enthusiast
Mar 10, 2024 · Databases

Why IN and NOT IN Should Be Avoided in SQL Queries

Because IN and NOT IN often bypass indexes on large tables, can yield incorrect results when column names differ or NULL values are present, and may cause severe performance penalties, they should be replaced with EXISTS/NOT EXISTS subqueries or appropriate JOINs, reserving IN only for small literal lists.

DatabaseIN clauseNOT IN
0 likes · 4 min read
Why IN and NOT IN Should Be Avoided in SQL Queries
php中文网 Courses
php中文网 Courses
Nov 9, 2022 · Databases

MySQL Slow Query Optimization: Live Demonstration on a Production To-Do List

This article walks through a real‑world MySQL slow‑query case, detailing analysis, index checks, character‑set alignment, forced index usage, and IN‑clause considerations that together reduced a 5‑second query to under one second.

IN clauseIndex OptimizationMySQL
0 likes · 4 min read
MySQL Slow Query Optimization: Live Demonstration on a Production To-Do List
360 Zhihui Cloud Developer
360 Zhihui Cloud Developer
Apr 11, 2017 · Databases

Why a Simple MySQL IN Subquery Takes 33 Seconds and How to Fix It

This article examines why a seemingly simple MySQL IN subquery on tens of thousands of rows can take 33 seconds, explains the optimizer’s behavior in MySQL 5.5, and presents practical fixes such as using temporary tables or JOINs to dramatically improve performance.

IN clauseMySQLOptimization
0 likes · 5 min read
Why a Simple MySQL IN Subquery Takes 33 Seconds and How to Fix It