Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!usc!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!hacgate!ashtate!dbase!awd
From: awd@dbase.UUCP (Alastair Dallas)
Newsgroups: comp.databases
Subject: Re: Clipper/dBase Seek Question
Summary: INDEX ON LTRIM(..) is a bad idea
Message-ID: <202@dbase.UUCP>
Date: 23 Aug 89 17:08:43 GMT
References: <238@fltk.UUCP> <20900014@silver>
Organization: Ashton Tate Devlopment Center Glendale, Calif.
Lines: 36

In article <20900014@silver>, blank@silver.bacs.indiana.edu writes:
> 
> Also, make sure that the number of spaces in front of the number are
> the same. In fact, all of these types of searches, I add a ltrim to
> avoid the problem:
> 
> index on ltrim(str(invnum))+"*"+ltrim(str(seqnum))
> seek ltrim(str(invnum))+"*"
> 
> -doug

INDEX ON LTRIM(..) is a bad idea.  It is very important that index keys be
fixed length, and TRIM() or LTRIM() do not support this:

.INDEX ON LTRIM(STR(N)) TO Foo
.LIST STR(N), LTRIM(STR(N)), LEN(LTRIM(STR(N)))

	1          13 13                2
        2       12345 12345             5
        3         233 233               3
        4         166 166               3
        5          32 32                2
        6           0 0                 1

Indexes must have fixed length keys.  Quoting the dBASE IV manual (p2-150):
"dBASE IV does not prohibit you from creating an index with a variable-length
key, but the index may not be reliable."

/alastair/



	N		STR(N)		 Key Length
	13		"13"		     2
	123456		"123456"	     6
	0