SDB - a simple database system                        Page 1


1.0  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.

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.



2.0  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.



3.0  COMMANDS

SDB recognizes the following commands:

     1.  Create a new relation

             create <rname> <alist> <size>

     2.  Insert tuples into a relation

             insert <rname>

     3.  Delete tuples from relations

             delete <rnames> [ where <boolean> ]

     4.  Update tuples within a relation

             update <anames> from <rnames> [ where <boolean> ]

     5.  Print tuples

             print <anames> from <rnames> [ where <boolean> ]
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     6.  Import tuples from a file

             import <file-name> into <rname>

     7.  Export tuples to a file

             export <rname> into <file-name>

     8.  Compress a relation file

             compress <rname>




4.0  AVAILABILITY

SDB  is  available  from  David   Betz   (NOVA::BETZ).    No
guarantees are given, but suggestions will be considered.