[cmrdporcupine]

A library written in SQL is called... a view. If you are repeating yourself in SQL to the extent you're reaching for a library, you might be doing it wrong. Take advantage of your DB's facilities instead of fighting it.

Or alternatively, if it's for things that really are mutating state and involving biz logic... a stored procedure.

Date & Darwin proposed the addition of "operators" to the relational algebra in their "Tutorial D" description of alternatives to SQL. That is, instead of "stored procedure", the addition of a type system matching on relations ("tables") and their tuples ("rows") and then the ability to create user-defined programmatic "operators" (a bit like OO methods) for those types.

[michaelmior]

I think the point was that it's not really easy to broadly share useful libraries of views or stored procedures. At one point Oracle was working on an integration that would allow you to package stored procedures written in JavaScript as node modules and then just install them to any database. Not sure what came of that.