/rdb is comprised of shell-level programs that read tables from the standard input and write tables to the standard output. All relational operators are supported as separate programs.
The project was abandoned as of 2016.
Relational
Command-line / Shell
http://www.rdb.com/
Revolutionary Software, Inc.
US
1984
2016
Commercial
Bash
BSD, Linux, OS X, Solaris, Windows
Proprietary