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Select into cursor nofilter option
Message
De
28/03/2002 08:04:32
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
 
 
À
27/03/2002 18:35:13
Information générale
Forum:
Visual FoxPro
Catégorie:
Autre
Divers
Thread ID:
00638193
Message ID:
00638330
Vues:
20
>VFP 7 doc states the following
>
>
>"Include NOFILTER to create a cursor that can be used in subsequent queries. In previous versions of Visual FoxPro, it was necessary to include an extra constant or expression as a filter to create a cursor that could be used in subsequent queries. For example, adding a logical true as a filter expression created a query that could be used in subsequent queries:
>
>SELECT *, .T. FROM customers INTO CURSOR myquery
>Including NOFILTER can reduce query performance because a temporary table is created on disk. The temporary table is deleted from disk when the cursor is closed. "
>
>But it never seemed to be problem( at least in VFP6 ) and it is not a problem in VFP7 for
>
>SELECT * FROM customers INTO CURSOR myquery
>select * from myquery where cust_id = some_id into cursor myquery1
>
>What is meant by "subsequent query" then ?
>
>Thank you
>Michael

As Jim says, if you omit NOFILTER, you may or may not create a separate cursor. I have had cases where the same sequence of SELECT commands worked well, and later didn't. So, to be safe, if you have a sequence of SELECT commands, always use NOFILTER on the first cursor.

Hilmar.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
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