squeal-postgresql VS squealgen

You may want to have a look at squeal that someone mentioned the other day in the comments of this post.

https://github.com/morphismtech/squeal, because, to my knowledge, it's the only option that both maintains deep type safety without losing the expressive power of SQL. It can even typecheck your database migrations. There's even a tool to generate the types of your schema based on an existing database: https://github.com/mwotton/squealgen

Yep, https://github.com/morphismtech/squeal does this too.

If you want an example of a type-safe SQL eDSL in Haskell that doesn't have those problems (and supports more Postgres features than esquelto), I'd recommend https://github.com/morphismtech/squeal.

https://github.com/morphismtech/squeal, because, to my knowledge, it's the only option that both maintains deep type safety without losing the expressive power of SQL. It can even typecheck your database migrations. There's even a tool to generate the types of your schema based on an existing database: https://github.com/mwotton/squealgen

Indeed, this is exactly what squeal does. You define (or generate from your schema) a type-level description of your tables, including whether each column can be null or not, and squeal type-checks your SQL queries, including checking whether those fields should be wrapped in a Maybe or not. In the linked documentation, note how the user_id and email fields are defined:

If the DB is Postgres, then this is actually probably a good usecase for Squeal, along with squealgen. It has a bit of a learning curve, but what you get is the ability to read an existing DB and generate a type-level schema from it automatically, which can then be used for completely type-safe queries. It also supports type-level migrations.