.title SDB - a simple database system
.first title
.hl 1 Introduction
SDB is a simple database manager for small systems. It was developed to provide
a relatively low overhead system for storing data on systems with limited disk
and memory resources. The current version runs on a PDT-11/150 with 2 RX01
floppy disk drives and 60K bytes of memory under the RT-11 operating system.
(it also runs on the VAX under VMS) It is implemented in DECUS-C and contains
a callable interface allowing programs written in DECUS-C to access SDB
databases.
.sk
SDB was originally intended to be a relation database system.
It should be noted that SDB is not a relationally complete system. It provides
the relational operations of SELECT, PROJECT, and JOIN, but does not provide
the set operations of UNION, INTERSECTION, or DIFFERENCE.
.hl 1 Relation file formats
SDB maintains a separate file for each relation that the user creates. This
file contains a header block containing the definition of the relation
including the names and types of all of the relation's attributes. The
remainder of the file contains fixed length records each containing one tuple
from the relation.
.hl 1 Commands
SDB recognizes the following commands:
.list
.le;Create a new relation
.sk
.lit
    create <rname> <alist> <size>
.end lit

.le;Insert tuples into a relation
.sk
.lit
    insert <rname>
.end lit

.le;Delete tuples from relations
.sk
.lit
    delete <rnames> [ where <boolean> ]
.end lit

.le;Update tuples within a relation
.sk
.lit
    update <anames> from <rnames> [ where <boolean> ]
.end lit

.le;Print tuples
.sk
.lit
    print <anames> from <rnames> [ where <boolean> ]
.end lit

.le;Import tuples from a file
.sk
.lit
    import <file-name> into <rname>
.end lit

.le;Export tuples to a file
.sk
.lit
    export <rname> into <file-name>
.end lit

.le;Compress a relation file
.sk
.lit
    compress <rname>
.end lit
.els
.hl 1 Availability
SDB is available from David Betz (NOVA::BETZ). No guarantees are given, but
suggestions will be considered.