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SQLa uses Zod’s TypeScript-first schema validation with static type inference capabilities to define data structures and introspects Zod’s type-safe schema to generates SQL. You can define tables, views, and other SQL DDL, DML and DQL statements using Zod then use SQLa to emit database-agnostic SQL. This way your data structures can be used with compile-type type checking but also be useful at runtime on the server or user agents like browsers and mobile apps.

Zod should be seen as the primary developer experience (DX) layer because it has some great extensions. For example:

  • if we need a JSON Schema generated from a SQL DDL definition, we can just use a Zod-to-JSON Schema library without inventing anything ourselves.
  • if we need utility functions to manage our Zod-based models try Zod Utilz Framework agnostic utilities.
  • before writing any new modeling infrastructure code, check the Zod ecosystem; if we do end up inventing something, build it on top of Zod whenever possible.


In order to allow Zod to manage our compile-type types and our runtime validation behaviors we need to create bridges between Zod types and SQLa SQL domains. There are different techniques for simple zod extensions vs. more advanced extensions.


The first, simple but usually effective, bridge between Zod and SQLa is render/domain/domain.ts:zodSqlDomainRawCreateParams which maps our custom JSON properties and stringifies them into Zod’s description field.

Zod Baggage

The second, more extensible, bridge between Zod and SQLa is a mapping layer called Zod Baggage, defined in lib/universal/zod-aide.ts. It’s marked universal since it can be used for other purposes but resides in this repo for convenience. The purpose of ZodTypedBaggage and zodBaggage is to allow arbitrary meta data called baggage to be stored with Zod types (usually scalars). Using this bridge library we can create SQL-specific data and store it alongside (literally inside the ZodType._def object).