Right, I'm just curious what the use case is where you want to be able to abstract over the connection for a variety of relational databases, but don't need to abstract over the differing syntax for the queries.
The use case would be the same as the one covered by jdbc and odbc. That is creating a standard interface to connect to databases at a lower level than the orm. This could then be used by an orm or query builder to communicate with the database. That’s how for example I can use Spring JPA and if I write either fairly portable sql or use the crud repository methods, I can connect to multiple different sql databases by simply providing a different jdbc URL.
How to handle the differing syntax of each databases would be handled at a higher level, by the query builder or orm. The orm could decide to let the user decide for themselves whether to write portable sql or not and fail at runtime, or like diesel in rust, enforce the useable features through its types.
In my experience that is something that is currently missing in the rust ecosystem. Each library seem to have its own connection logic and if I want to write a program that could run on different databases in rust right now, I have to write different code to connect to each database I would like to support.
Diesel has been serving me really well but I currently need to choose a specific backend when I am building a query, and implementing the above dynamic style of connection would be quite cumbersome to implement. It would be nice if we could choose another a standard sql backend where I would only be able to use a subset of features supported by most sql databases and build queries against that. Hopefully the RDBC project could help with something like that.
One is data analysis. I often have data in two or three different datastores that I need to analyze together (a column-oriented DB, one or more row-oriented DBs, a key-value store, a document store, a Hadoop/Spark cluster) and it's nice to be able to use the same code to open and manage connections to any one of them. My queries are and always will be vendor-specific, but my connection handling is all just generic ODBC code.
It's also great for WYSIWYG BI tools like Tableau or Power BI, which can connect to and fetch results from anything that has an ODBC driver. Without that, the BI tool vendor would need to write their own driver specific to each datastore on the market. So if anyone ever wants to build a generic BI/analytics tool product in Rust, this is a prerequisite.
