kysely-typescript

name	kysely-typescript
description	Type-safe SQL query building in TypeScript using Kysely. Use when writing or reviewing Kysely queries, schema types, migrations, raw SQL snippets, dynamic filters, conditional selects, transactions, or reusable query helpers.

Kysely TypeScript Knowledge Hub

Use Kysely so TypeScript describes the SQL you are actually going to run. Preserve inference by default; when a query must become dynamic or raw, make the unsafe boundary small, typed, and reviewable.

Applicability Gate

Apply this skill when ANY of the following are true:

• The user asks to write or modify a database query using Kysely
• The user is designing a TypeScript schema for Kysely (the Database interface)
• The user asks whether Kysely code is still type-safe
• The user uses raw SQL, dynamic identifiers, conditional selects, or reusable helpers
• The user encounters a type instantiation error in a Kysely query
• The user asks how to build dynamic queries, CTEs, or reusable query helpers
• The user needs to write a database migration using Kysely

Do NOT apply when:

• The task is generic TypeScript quality with no Kysely or SQL surface
• The task is ORM relation modeling; Kysely is a query builder, not an ORM

Routing Table

Question	Route to
"How should I keep this Kysely code type-safe?"	references/type-safety-first.md
"How do I define my database interface or get started?"	references/getting-started.md
"How do I align TypeScript types with what the DB returns?"	references/data-types.md
"How do I build queries conditionally based on variables?"	references/conditional-queries.md
"How do I fix 'Type instantiation is excessively deep'?"	references/troubleshooting.md
"How do I reuse joined tables safely without duplicating?"	references/deduplicate-joins.md
"How do I compile queries without executing them?"	references/execution-flow.md
"How do I write raw expressions, function calls, or subqueries?"	references/expressions.md
"How do I write a custom dialect or use a plugin?"	references/extending.md
"How do I query Kysely's introspection or relation metadata?"	references/relation-metadata.md
"How do I log queries or debug SQL output?"	references/logging.md
"How do I write Kysely database migrations?"	references/migrations.md
"How do I write raw SQL or use the sql template tag?"	references/raw-sql.md
"How do I map or use database relations?"	references/relations.md
"How do I extract query logic into reusable functions?"	references/reusable-helpers.md
"How do I pass query builders between functions?"	references/splitting-queries.md
"How do I use DB schemas (like Postgres 'public')?"	references/schemas.md

Procedure

1. Identify the task type. What is the user trying to do with Kysely?
2. Load the type-safety policy when it matters. Read references/type-safety-first.md for schema design, raw SQL, dynamic filters, conditional selects, reusable helpers, type errors, or Kysely code review.
3. Route to the right reference. Use the routing table above. Read only the reference file(s) needed — do not load all.
4. Apply the methodology. Follow the normative rules from the loaded reference.
5. Verify the boundary. Check that strict TypeScript accepts the query and that declared column types match the runtime values returned by the driver.

Confirmation Policy

Do NOT execute destructive migrations or large schema changes without explicit user confirmation. Present proposed code as diffs and wait for approval.