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Join.doc
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1994-03-13
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join - Relational database operator
Syntax
join [options]... file1 file2
Description
Join forms, on the standard output, a join of two relations represented
by file1 and file2. If only one file is specified the standard input is
used as file1.
The files must be sorted on the field that is to join them; usually this
is the first field.
There is one output line for each pair of lines in file1 and file2 that
have identical join fields. The output normally consists of the join
field followed by the rest of the line from file 1 then the rest of the
line from file2
Fields are normally separated by white space. Multiple separators count
as one and leading separators are discarded.
Options
-a=n In addition to the normal output, produce a line for each
unpairable line in file n.
-e=s Replace empty output fields with string s.
-j=n.m Join file n on field m. This option may appear twice.
-f=n.m The output line contains field m from file n.
The -f parameter may appear up to 256 times.
A field may occur more than once in the list.
-i=n.c Input fields in file n are separated by c. Each ocurrence
of c delimits a field. The default is whitespace.
-o=c Output fields are separated by c. The default is a tab.
Bugs
There may be no more than 256 fields in a record.
The maximum size of a record is 4096 characters.
The options available differ somewhat from the UNIX version:
-j parameter format is different.
-f replaces the unix -o parameter and has a different parameter format.
-i )
-o ) both replace the -t parameter and use a different parameter format.
These changes were made to add flexibility to the file formats and to
allow more flexibility in option specification.
Author
Martin Gregorie
10 Sadlers Mead
Harlow
Essex CM18 6HG
Gregorie@LFGMS.logica.com