JEQL Query Language
The JEQL Query Language is a language
which supports processing tabular data structures.
The 'E' in JEQL stands for all of the following:
- Extended - JEQL provides extensions to SQL to make it more powerful for processing data
- Embeddable - The JEQL engine can be embedded in other applications to provide a query language for table-oriented data models
- ETL - Extract/Transform/Load is a major use case for JEQL
- Efficient - JEQL's implementation makes development and execution faster!
Features
The JEQL language and engine has the following significant features:
- JEQL supports tables as first-class data structures.
This allows using the paradigm of
Table-Oriented Programming
- Tables are processed using query statements expressed
using the familiar and well-understood SQL syntax and semantics.
- The version of SQL used in JEQL has many extensions designed to make it easier
to express common processing tasks.
Some extensions are taken from other SQL dialects.
Others are unique to JEQL
(such as table-valued constants, table-valued functions,
and an Internal WITH clause allowing intermediate expressions in select column lists).
- SQL queries are expressions in the JEQL language.
This makes it easy to chain multiple queries to accomplish a processing task.
- Tables in JEQL are loaded and queried with stream semantics.
This allows datasets larger than main memory to be processed.
- JEQL supports all usual Java scalar datatypes (ints, Strings, doubles) and some useful complex ones (Date).
- JTS Geometry is a standard built-in type,
along with a wide set of spatial functions, predicates constructors,
and aggregate functions.
This makes JEQL an excellent tool for processing spatial datasets.
- JEQL can read and write tabular data from a variety of file formats
(including Text, CSV, DBF and ESRI Shapefiles)
and databases (including any JDBC-compatible database).
It is easy to add I/O commands for new data sources.
- Because JEQL has tables as a native datatype,
there is no "impedance mismatch" issue with accessing tabular datasources.
This greatly simplifies working with external data.
- JEQL is easily extensible with new functions and commands, provided as Java classes.
Extensions are loaded dynamically, without any recompilation of the JEQL engine.
- The JEQL engine is supplied with a standalone script interpreter.
It is also designed to be easily embeddable in other applications
to provide scripting and data manipulation capability
for custom tabular data models
- The JEQL interpreter is written in 100% pure JavaTM
Examples
See examples of JEQL functionality.
Software
The latest JEQL version is
here.
Support
There is a JEQL group mailing list here.
Design, bug reports, new release etc, are all discussed on this list.
Documentation
Note: Documentation is under ongoing development.
License
JEQL is released under the GPL license.
JavaTM is a trademark of Sun
Microsystems, Inc. in the United States and other countries.