Individual skill
mysql
Use when designing, querying, indexing or operating a MySQL or MariaDB database and engine-specific behaviour matters — schema and type choices, index design, reading EXPLAIN, online schema change, replication and replica lag, locking and InnoDB deadlocks, charset traps, and server config. NOT portable SELECT/JOIN/window-function craft (that is `sql`), NOT PostgreSQL engine behaviour like VACUUM or JSONB (that is `postgresdb`), NOT the PlanetScale/Vitess branch-and-deploy workflow (that is `planetscale`).
skills/mysql/SKILL.md
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- Nov 4, 2026
- License
- MIT
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- mysql Declared skill tag
- mariadb Declared skill tag
- innodb Declared skill tag
- explain Declared skill tag
- replication Declared skill tag
- indexing Declared skill tag
- online-ddl Declared skill tag
- database Declared skill tag
- data Derived category
- design Derived category
- operations Derived category
- data-databases Derived category
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SKILL.mdcore · 15,048 bytesSKILL.mdcore · 15,048 bytesSKILL.mdcore · 15,048 bytesevals/README.mddoc · 983 bytesevals/cases.yamlasset · 3,540 bytesreferences/indexing-and-explain.mddoc · 7,522 bytesreferences/mysql-vs-mariadb.mddoc · 4,735 bytesreferences/online-ddl-and-migrations.mddoc · 6,074 bytesreferences/replication-and-ha.mddoc · 5,587 bytesscripts/verify.shruns · 6,724 bytes
Read excerpt
# MySQL / MariaDB engine
You are working below portable SQL, at the layer where the answer depends on *which engine* is
running. This skill owns MySQL 8.4 LTS and MariaDB 11.8 LTS: the **InnoDB** clustered-index storage
model, MySQL-flavoured DDL and types, index design and the leftmost-prefix rule, reading `EXPLAIN`
and fixing the plan, online DDL, replication, locking/deadlocks, and day-2 server config.
The dividing line is simple: **if the answer is identical on PostgreSQL, it belongs in `sql`, not
here.** `sql` owns the dialect-independent SELECT grammar. `mysql` owns how *this* engine stores,
plans, locks, and replicates. `postgresdb` is the peer engine for the other database — same body
shape, different facts, never the same answer.
## When to use
