What is this?
Kysely (pronounced 'Key-Seh-Lee') is a type-safe, autocompletion-friendly SQL query builder for TypeScript, inspired by Knex.js: it checks your queries at compile time and types the results.
Kysely (pronounced 'Key-Seh-Lee') is a type-safe, autocompletion-friendly SQL query builder for TypeScript, inspired by Knex.js: it checks your queries at compile time and types the results.So it's a library I add to my project, not a tool I run?Exactly — a library. You write queries in your TypeScript code, Kysely builds the SQL, and the rows that come back are fully typed.
Exactly — a library. You write queries in your TypeScript code, Kysely builds the SQL, and the rows that come back are fully typed.Where does it run — is Node.js the only option?Node.js is the main target (Node 22+ per its package metadata), but it also runs on Deno, Bun, Cloudflare Workers and in web browsers — and the package ships without runtime dependencies.
Node.js is the main target (Node 22+ per its package metadata), but it also runs on Deno, Bun, Cloudflare Workers and in web browsers — and the package ships without runtime dependencies.What if part of my query can't be typed at compile time?Kysely has escape hatches for exactly those cases: the sql template tag for raw SQL and the DynamicModule for dynamic situations.
Kysely has escape hatches for exactly those cases: the sql template tag for raw SQL and the DynamicModule for dynamic situations.Do I need a TypeScript project for this to make sense?Yes — it is built for TypeScript codebases: the compile-time checks and autocompletion come from static types. You could call it from plain JavaScript, but you would lose the type safety that is the whole point.
Yes — it is built for TypeScript codebases: the compile-time checks and autocompletion come from static types. You could call it from plain JavaScript, but you would lose the type safety that is the whole point.What does the type safety actually buy me?Compile-time guarantees: you can only reference tables and columns visible at that point of the query, and the result type contains exactly the selected columns with correct types and aliases — plus autocompletion while you write.
Compile-time guarantees: you can only reference tables and columns visible at that point of the query, and the result type contains exactly the selected columns with correct types and aliases — plus autocompletion while you write.How smart is it about aliases and subqueries?Very: it parses an alias like pet.name into a typed petname column in the result row, and infers column names, aliases and types from selected subqueries, joined subqueries and with statements.
Very: it parses an alias like pet.name into a typed petname column in the result row, and infers column names, aliases and types from selected subqueries, joined subqueries and with statements.Which databases does it support?Its repo topics list PostgreSQL, MySQL, SQLite and Microsoft SQL Server (MSSQL).
Its repo topics list PostgreSQL, MySQL, SQLite and Microsoft SQL Server (MSSQL).How do you pronounce the name?'Key-Seh-Lee' — the README settles that in its first line.
'Key-Seh-Lee' — the README settles that in its first line.Which topics is it in?query-builder, type-safe, mssql, autocomplete, deno, bun, mysql, sql, sqlite, postgresql, browser, backend
query-builder, type-safe, mssql, autocomplete, deno, bun, mysql, sql, sqlite, postgresql, browser, backend