How to learn Alf?
This documentation comes with a lot of examples that you can try online. This is probably one of the most efficient ways to learn. More specifically, here is a possible roadmap:
- Start with the documentation of a relational operator,
- Try the examples, play with them,
- Read the description and implementation notes,
- Try to understand the definitions when an operator can be defined in terms of other operators. Those definitions use the closure property of relational algebra a lot. From there, jump to another operator.
- If needed, have a look at predicates and other concepts to better understand the language and operator signatures.
The query language aims at being as intuitive as possible, even if some background is definitely needed. Two main directions here:
- Make sure to eventually read the relational basics.
- If you do not know ruby, make sure to eventually read the ruby basics.
How to get started outside of try-alf.org ?
Alf comes as a ruby gem. You need ruby >= 1.9.3.
gem install alf [sqlite3] [pg]
Once installed, the command line tool is available:
alf --help alf --examples show suppliers alf --db="postgres://user:password@host/database" show tablename