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The best way to use a portion of a field for indexing
Message
From
11/01/2005 06:02:22
 
 
To
11/01/2005 05:54:46
General information
Forum:
Visual FoxPro
Category:
Databases,Tables, Views, Indexing and SQL syntax
Environment versions
Visual FoxPro:
VFP 6 SP5
OS:
Windows XP SP2
Network:
Windows 2000 Server
Database:
Visual FoxPro
Miscellaneous
Thread ID:
00975802
Message ID:
00975971
Views:
34
>>Hi Walter,
>>
>>yes, but it your case, why? INDEX ON FirstName-LastName gives EXACTLY the same result! One of the little used features of xBase.
>
>This is not true:
>
>FirstName-LastName
>is
>PADR(RTRIM(FirstName)+LastName,FSIZE(FirstName)+FSIZE(LastName))
>
>
>>
>>OK, I admit I should have use the word "as", and not "in". 'Never use alltrim as an index expression. Thank you for the correction.
>>
>>>Hi Tore,
>
>Then:
>
>Never use LTRIM()
Correct

>Never use RTRIM()
Correct

>and then
>NEVER USE OF A VARCHAR FIELD ON VFP9 !
Wrong. A varchar field has a maximum length which will be the key length

>
>The issue appear when you use this into a primary/candidate index,
>and this is true for cExp1-cExp2 also.
>
>For a search text index, ALLTRIM(),LTRIM()... can to be used without problems.
If you like to live dangerously, yes. VFP will calculate the index key length by evaluating the index expression on the first record. So, if the first records gives a key length of 0, your index will be of no value.

>
>Fabio
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