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What is better and faster
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17/01/2005 16:10:48
 
 
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Versions des environnements
Visual FoxPro:
VFP 8 SP1
OS:
Windows XP SP2
Divers
Thread ID:
00977833
Message ID:
00977850
Vues:
24
You may need to take into account that you will need to modify the code for the second option if you ever increase the length of one of the fields in the table. You may get incorrect results otherwise.

>In the Names table we have cl_Name C(25), cf_Name C(20), cM_Initial C(1) fields. If I want to search by last name and first name I can use:
>
>
>SET ANSI OFF
>select ... from ... where cl_name ="GREE" and cf_name = "MAR" and cM_Initial = ""
>
>or I can use
>lcName = padr("GREE",25,"_") + padr("MAR",20,"_")+padr("",1,"_")
>select ... from ... where cl_name + cf_name + cm_Initial LIKE lcName
>
>
>I currently put the following indexes in my local copy of Names table:
>
>cl_name
>cf_name
>cm_initial
>
>cl_name+cf_name+cm_initial
>
>Today I re-coded from the first approach to the second and it seems to me that I slowed down my searches considerably.
>
>I think, in either case we do not need to have an index on cm_Initial (it looks stupid to have an index on 1 char field).
>
>What do you think? I would appreciate your input.
>
>I've done the same with the Phone (we have separate fields for different phone parts). I haven't tested this change yet.
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