How to Fix MySQL "Out of Memory" Crash During Large ALTER TABLE Migration
Running an ALTER TABLE on a large table crashes the MySQL server outright with an out-of-memory error, rather than just running slowly. Certain schema changes...
Category
MySQL
Fixes for connection limits, query performance, and encoding issues in MySQL.
How to Fix MySQL JSON_EXTRACT Query Not Using Functional Index in MySQL 8
You've created a functional index specifically to speed up queries filtering on a value inside a JSON column, but EXPLAIN shows MySQL is still doing a full...
How to Fix MySQL "Client Does Not Support Authentication Protocol Requested by Server"
An older MySQL client — a legacy application, an outdated driver, or an older command-line tool — fails to connect to a newer MySQL server with an...
How to Fix "Error 1045 (28000): Access Denied for User 'root'@'localhost'"
You try to connect to MySQL as root and get rejected outright, even with a password you're sure is correct. Error 1045 means MySQL received your connection...
How to Fix "MySQL Server Has Gone Away" Error During Query Execution
A query that was working fine suddenly fails mid-execution with MySQL claiming the server disappeared, even though MySQL is clearly still running and other...
How to Resolve "Error 1215 (HY000): Cannot Add Foreign Key Constraint"
Creating or altering a table to add a foreign key fails with a vague error that doesn't say what's actually wrong. Error 1215 is famously unhelpful on its own...
How to Fix "Too Many Connections" Error in MySQL Production
Your application starts failing to connect to MySQL during peak traffic, and the server itself is rejecting new connections outright. This means every...
How to Resolve "Incorrect String Value" UTF8 Encoding Error in MySQL
Inserting text containing emoji, certain non-Latin characters, or specific Unicode symbols fails with an encoding error, even though your table is already...
How to Fix "Out of Memory (Needed X Bytes)" Error in MySQL
MySQL refuses to run a query or crashes outright, reporting it needed a specific number of bytes it couldn't allocate. This means MySQL's memory usage,...