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Monster Media 1993 #2
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PRESSDB.DOC
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1993-03-14
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EXTERNAL DATABASE FUNCTIONS
A. COMPRESS - Rewrite existing databases to optimize data
B. EXTRACT - Extract data from a database to the screen or a file
C. DB2DBF - Export data from a database to a dBase III file
D. DBF2DB - Import data from a dBase III file
A. COMPRESS - compress a data base
External usage: pressdb databasename [-i indexname] [-s blocksize]
pressdb compresses all the deleted data and unused space out of the
data file of the ISAM (or LDM) database named "databasename". The
"databasename" is the name of the database to compress (any extent is
ignored). It may include a drive specifier and/or a pathname. The
compression is done by copying the records to a temporary file,
deleting the original file, then renaming the temporary file to have
the original name.
The arguments in square brackets [like this] are optional. If you do
not specify any arguments at all, the program prompts you for them.
The "-i indexname" (index) option tells the program to copy the
records in the order of the index "indexname" instead of the Physical
Index. Otherwise, the records are copied to the new data file in
Physical Index order.
The "-s blocksize" (size) option tells the program to make the new
data file with a block size of "blocksize". Otherwise, the new,
compressed data file has the same blocksize as the original data file.
To compress the "maillist" database, copying in "zip code" index
order, with a new block size of 1024, type:
pressdb maillist -i "zip code" -s 1024
COMMAND BAR
-----------
In the Database, the COMPRESS option will perform database rewrites
on the following databases and tre respective indexes:
Database Index Index by:
GUNS Database: GUN1 Manumod Manufacturer, Model
DEALER Deal State, City, Name
MANUF Comp State, City, Name
INVENT sdateIDX Sales Date, Manufacturer,
Model
It is a good idea to rewrite a database after additions or
deletions are made. The databases above require about 3-5 minutes
to rewrite. The function takes you into the gun database (most
likely the largest database) just to make sure the writing process
was successful.
The other database tools, Import, Export, and Dumpdb must be run
standalone due to input and redirect issues. These functions are
described below.
B. EXTRACT - tools program to dump data from database
External usage: dumpdata databasename [-i indexname]
dumpdata prints the records of the ISAM (or LDM) data file from the
database named "databasename" to stdout in human readable form. You
may redirect stdout to a disk file or to the printer in the usual way.
The printing is done via the showrec ISAM routine.
"databasename" is the name of the database to be printed (any extent
is ignored). It should include a drive specifier and/or a pathname
if the file is not in the current directory on the current drive.
The "-i" (indexname) argument is optional. It tells the program to
print the records in the order of the index named "indexname".
Otherwise, the data records are printed in Physical Index order.
If you do not specify any arguments at all, the program prompts you
for them.
To print the data records from the "maillist.db" file in "zip code"
order, type:
dumpdata maillist -i "zip code"
To print the data records from the "maillist.db" file in "zip code"
order to a file ( file.doc in this example ), type:
dumpdata maillist -i "zip code" >file.doc
To print the data records from "maillist.db" to the printer, type:
dumpdata maillist >prn:
C. EXPORT - convert an isam file to a Dbase III file
Standalone usage: dbtodbf dbname [dbfname] [-i indexname]
dbtodbf converts an ISAM DB file to an existing dBASE III DBF file
by copying the ISAM records to the dBASE file in Physical Index order.
No indexes are copied. "dbname" is the name of the ISAM file to
convert. It should include a drive specifier and/or a pathname if the
file is not in the current directory on the current drive.
The arguments in square brackets [like this] are optional. If you do
not specify any arguments at all, the program prompts you for them.
"dbfname" is the name of the dBASE file to write to. If you don't
specify a "dbfname", the program assumes that the dBASE file has the
same name as the ISAM file but with a ".dbf" extent. The ".dbf" file
MUST ALREADY EXIST and the converted ISAM records are appended to it.
You can use the dBASE program to create the dBASE file. The "dbfname"
may include a drive specifier and/or a pathname.
Only fields whose names match exactly (except for upper/lower case)
are copied. The order of the fields may be different in the two files.
All field values are padded to the appropriate field size, since dBASE
supports only fixed length records.
The "-i indexname" option tells the program to copy the records in the
order of the index named "indexname", instead of in Physical Index
order.
To convert records from an ISAM file named "newlist.db" to the
existing dBASE file named "newlist.dbf" in the order of the "zip code"
index, type:
dbtodbf newlist -i "zip code"
D. IMPORT - convert a dBASE III file to an isam file
External usage: dbftodb dbfname [dbname] [-a] [-b] [-d] [-n]
dbftodb converts a dBASE III DBF file to an ISAM DB file by copying
the dBASE records to the ISAM file in physical order. No ISAM indexes
are created (except the automatic Physical Index). You can use the
Little Data Manager program (LDM) to create indexes for the converted
file. dbftodb can copy records to an existing ISAM DB file, or you
can create a new ISAM DB file.
"dbfname" is the name of the dBASE file to convert. It should include
a drive specifier and/or a pathname if the file is not in the current
directory on the current drive. The arguments in square brackets [like
this] are optional. If you do not specify any arguments at all, the
program prompts you for them.
The "dbname" is the name of the output file containing the converted
records. It may include a drive specifier and/or a pathname. If you
specify a "dbname", the ISAM records are written to that file. If you
do not specify a "dbname", a file is created using the same root name
as the dBASE file with a ".db" extent. In either case, if the ISAM
file already exists, only those fields whose names match in both files
are converted. If the ISAM file does not already exist, it is created
to have the same fields in the same order as in the dBASE file, and
every dBASE field (except memo fields) is converted.
You may create the ISAM file beforehand with the LDM program or with
your own application program. The ISAM file may include additional
fields not in the dBASE record format; these fields are left blank
during the conversion of new records. The ISAM file does not have to
include every field from the dBASE file; only fields whose names match
are copied.
The fields in the ISAM record format may be in a different order than
in the dBASE record format. The field names must match character by
character, except that case (upper or lower) is not significant.
The -a (append) option tells the program to append records to the ISAM
file if the ISAM file already exists. If you do not use the -a option
and there is already an ISAM file, the program prompts you to append
to the file, overwrite the file, or abort the program.
The -b (boolean) option tells the program to store false booleans as
an empty field (zero length). This saves some space in the ISAM file
if you have many records with false boolean values. Otherwise,
boolean values from the dBASE file are stored as "T" for true and
"F" for false.
The -d (date) option tells the program to store only the last two
digits; for example, "88". Otherwise, the year part of a date field
is stored with all four digits; for example, "1988".
The -n (numeric) option tells the program to strip leading blanks from
numeric fields. Otherwise, leading blanks in numeric fields are
preserved.
Leading and trailing blanks are stripped from all character fields.
To convert records from a dBASE file named "maillist.dbf" to a new
ISAM file named "newlist.db", store False booleans as empty fields,
and store only the last two digits of the date fields, type:
dbftodb maillist newlist -b -d