Use a database with Clojure

Question

What methods to use a database from Clojure are there?

I know from Clojure you can do anything you can with Java, but that means that I may end up using something overly

Answer 1

The latest and greatest for SQL databases seems to be HoneySQL and Yesql.

HoneySQL is a quite elegant DSL to generate SQL queries. There are rumours it can even modify the statements to be highly optimized, see the clojure-group thread "Current best-of-breed JDBC libraries?" from Feb 24 2015.

Niels van Klaveren says in the above-mentioned thread:

"Basically, it [HoneySQL] generates SQL scripts to relink foreign key references to clean up duplicates in a database. It takes a honeysql select query with (at least) a from table, a group-by and an order-by clause as a base definition what are to be considered doubles, and in which order records should be preserved. In combination with JDBC metadata that query effectively gets rewritten to generate:

• A temporary replacement table
• Queries to unify unique indexes, to prevent clashes when foreign key references are updated
• Queries to update all foreign key references
• Delete statements to remove all duplicates

To create the best performing, but still database independent SQL, I had to extend honeysql with extra clauses like OVER and PARTITION BY. I wouldn't say it was a breeze, but seemed to work very well.

...

That cut down SQL to (sometimes) GB's of script to around a few 100 lines of SQL, and on one occasion, a runtime from 19 hours to 1.5 minutes."

Yesql, on the other hand, aim for total simplicity. It defines some functions to load parameterized .sql-files.

It's webpage mentions the following "USPs":

• No syntactic surprises. Your database doesn't stick to the SQL standard - none of them do - but Yesql doesn't care. You will never spend time hunting for "the equivalent sexp syntax". You will never need to fall back to a (raw-sql "some('funky'::SYNTAX)") function.
• Better editor support. Your editor probably already has great SQL support. By keeping the SQL as SQL, you get to use it.
• Team interoperability. Your DBAs can read and write the SQL you use in your Clojure project.
• Easier performance tuning. Need to EXPLAIN that query plan? It's much easier when your query is ordinary SQL.
• Query reuse. Drop the same SQL files into other projects, because they're just plain ol' SQL. Share them as a submodule.