TiDB SQL (MySQL-compat-focused)

Goal: generate SQL that runs correctly on TiDB by default, and avoid "works on MySQL but breaks on TiDB" constructs.

Workflow (use every time)

1. Identify the target engine and version:
   • Run SELECT VERSION();
   • If the result contains TiDB, treat it as TiDB and parse the version (needed for feature gates like Vector / Foreign Key).
   • If connecting to TiDB Cloud, ensure the client enables SSL with certificate + identity verification (see skills/tidb-sql/references/tidb-cloud-ssl.md).
2. Ask 2 quick capability questions if the request depends on them:
   • "Do you have TiFlash?" (needed for vector indexes)
   • "Is this TiDB Cloud Starter/Essential in a supported region for Full-Text Search?" (availability is limited)
3. Generate SQL using TiDB-safe defaults:
   • Avoid unsupported MySQL features (procedures/triggers/events/UDF/GEOMETRY/SPATIAL, etc.)
   • Treat views as read-only
   • Treat primary key changes as migration/rebuild work
4. If the user provides MySQL SQL, do a compatibility pass:
   • Replace unsupported features with TiDB alternatives
   • Call out behavior differences and version prerequisites explicitly
5. If SQL is slow or fails unexpectedly, use TiDB-native diagnostics:
   • Use EXPLAIN FORMAT = "tidb_json" for structured plans and operator trees.
   • Use EXPLAIN ANALYZE to compare estRows vs actRows (it executes the query).
   • If the plan looks wrong, consider ANALYZE TABLE ... to refresh statistics.

High-signal differences (keep in mind)

• Vector: TiDB supports VECTOR / VECTOR(D) types and vector functions/indexes; MySQL does not.
• No GEOMETRY/SPATIAL: avoid GEOMETRY, spatial functions, and SPATIAL indexes.
• No procedures / functions / triggers / events: move logic to the application layer or an external scheduler.
• Full-text search (TiDB feature): use TiDB full-text search SQL when available; don't assume MySQL FULLTEXT works everywhere.
• Views are read-only: no UPDATE/INSERT/DELETE against views.
• Foreign keys: supported in TiDB v6.6.0+; otherwise, don't rely on FK enforcement.
• Primary key changes are restricted: assume "create new table + backfill + swap" for PK changes.
• AUTO_RANDOM: prefer AUTO_RANDOM over AUTO_INCREMENT for write-hotspot avoidance when appropriate.
• Transactions: TiDB supports pessimistic and optimistic modes; handle optimistic COMMIT failures in application logic.

Use these references (inside this skill)

• skills/tidb-sql/references/vector.md - VECTOR types, functions, vector index DDL, and query patterns.
• skills/tidb-sql/references/full-text-search.md - Full-text search SQL patterns and availability gotchas.
• skills/tidb-sql/references/auto-random.md - AUTO_RANDOM rules, DDL patterns, and restrictions.
• skills/tidb-sql/references/transactions.md - pessimistic vs optimistic mode and session/global knobs.
• skills/tidb-sql/references/mysql-compatibility-notes.md - other "MySQL vs TiDB" differences that commonly break SQL.
• skills/tidb-sql/references/explain.md - EXPLAIN / EXPLAIN ANALYZE usage, tidb_json and dot formats.
• skills/tidb-sql/references/flashback.md - FLASHBACK TABLE/DATABASE and FLASHBACK CLUSTER recovery playbooks.
• skills/tidb-sql/references/tidb-cloud-ssl.md - TiDB Cloud SSL verification requirements and client flags.