ADQL

What is it?

ADQL: Astronomical Data Query Language

ADQL is the language used by the IVOA to represent astronomical queries posted to VO services (e.g. TAP). It is based on the Structured Query Language (SQL), especially on SQL-92 (see also an online BNF version for an easy navigation). The VO has a number of tabular data sets and many of them are stored in relational databases, making SQL a convenient access means. Thus, a subset of the SQL grammar has been extended to support queries that are specific to astronomy.

Status?

The last stable version is REC-2.1.

See also the section Releases of this GitHub Repository.

What about this repository?

This GitHub repository contains the sources of the IVOA document describing ADQL.

Only the LaTeX version is available here. No output version (e.g. PDF, HTML, DOC) should be stored in this repository.

A PDF preview is automatically generated by a GitHub workflow. It is accessible either by clicking of the above "Preview" badge or by looking at the pre-release "Auto updated PDF".

An HTML version of the BNF is also directly available in this repository: check out adql-bnf.html. It is generated from adql.bnf by the Makefile target named bnf. This latter uses the Perl script bnf2html.pl, originally coming https://ronsavage.github.io/SQL/ and customized for the ADQL purpose. Thanks to Mark Taylor for his research, time and efforts for providing this generator. Note that the HTML version of the BNF may be later automatically generated by a GitHub workflow.

Want to contribute?

1. Raise a GitHub Issue on this repository

2. Fork this repository (eventually clone it on your machine if you want to)

3. Create a branch in your forked repository ; this branch should be named after the issue(s) to fix (for instance: issue-7-add-license)

4. Commit suggested changes inside this branch

5. Create a Pull Request on the official repository (note: a git push is needed first, if you are working on a clone)

6. Wait for someone to review your Pull Request and accept it

This process has been described and demonstrated during the IVOA Interoperability Meeting of Oct. 2019 in Groningen ; see slides)

License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.