postgresql-typed VS sequelts

If you need Cassandra specifically, cql-io is pretty good. For a general purpose database I'd go with Postgres. There are many good choices in the Haskell ecosystem, but I really like postgres-typed. It lets you write plain SQL, checks you queries against a live database schema at compile time, and makes sure you use the results correctly as well. It's amazing, I never ran into type related errors and it's pretty seamless.

You can use these template literal types + infer to build an entire SQL parser. I did a POC that infers SQL query types by parsing the SQL query on a type level:

https://github.com/nikeee/sequelts

However, building this parser is pretty cumbersome and supporting multiple SQL dialects would be lots of pain. While I'm not a fan of query builders per se, Kysely pretty much covers everything that my POC tried to cover (except that 0 runtime overhead). However, you get the option to use different DBMs in tests than in production (pg in prod, sqlite in tests), which is a huge benefit for a lot of people. sequelts was designed to work with sqlite only. And it's not a hack.

The only thing I can imagine where this would be useful is when you don't have control about what DB is being used, for example, when building a product that should be compatible with Postgres and MariaDB (and each is getting used). However, in the age of containerization, this isn't a big problem any more.

In some ORMs, I need to create types that the result of a query containing JOINs is mapped to. Others don't support them _at all_. In TypeORM, there is a query builder which forces you to put in _some_ SQL for things like "WHERE a in (b, c)".

I created a proof of concept of a different approach: Just embrace SQL and provide static typing based on the query. The return type of a query is whatever that thing is that the query returns in the context of the database schema. It's possible to do in TypeScript, by parsing the SQL query at development time:

https://github.com/nikeee/sequelts

One benefit is that it does not need any runtime code, as it's just a type layer over SQL. You don't have to rely on some type-metadata that TypeScript emits. That's why it also works with JavaScript only.

I don't like ORMs that use runtime types either. Most of the time, I want to write raw SQL.

So as an experiment, I created a library that statically types raw SQL:

https://github.com/nikeee/sequelts

The idea is to parse the SQL queries using TS's type system. The parsed query is combined with the database schema and therefore, we know what type the query will return.

This is especially useful due to TS's structural type system.