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Select Statement appears to be filtering
Message
De
30/06/2006 16:28:58
 
 
À
30/06/2006 14:13:27
Mike Yearwood
Toronto, Ontario, Canada
Information générale
Forum:
Visual FoxPro
Catégorie:
Codage, syntaxe et commandes
Versions des environnements
Visual FoxPro:
VFP 9 SP1
OS:
Windows XP SP2
Network:
Windows 2003 Server
Database:
Visual FoxPro
Divers
Thread ID:
01132775
Message ID:
01133197
Vues:
21
>>>>>All,
>>>>>
>>>>>I am querying a VFP table that has about 1.5 million records. The table is indexed on a date field called aaddb. My query shows that it returned 13,533 records on the status bar. Then the status bar message changes and it states: Tcursor(c:\arrestees.dbf) Record: 24/1427204.
>>>>>Only the records I have selected show in the browse window. However if I do a ?reccount() it shows that there are 1427204 records in my cursor. If I select all of the records from the cursor into a new cursor I get all 1427204 records from the original table.
>>>>>
>>>>>This is my query.
>>>>>
>>>>>SELECT * FROM arrestees where BETWEEN(aaddb, CTOD('12/30/1939'), CTOD('12/29/1941')) into cursor tCursor
>>>>>
>>>>>
>>>>>How can I get just the records I am trying to select? This is a new one on me.
>>>>
>>>>That's a long-known issue. If the query is 100% rushmore optimizable, vfp may just do a SET FILTER. I have been adding NOFILTER to every query for many years now.
>>>
>>>Personally I add READWRITE in stead of NOFILTER. The net result is the same plus the new cursor is read/write.
>>
>>Personally I put them both in. Aiming to leave no doubt with the reader.
>
>That's a good point, but if a cursor is not going to be updated, I still put nofilter, just don't include readwrite. Readwrite must do more than just NOFILTER?

AFAIK READWRITE was introduced in a later version than NOFILTER, and READWRITE makes NOFILTER redundant. READWRITE simply sets a flag on the cursor, so the overhead of using READWRITE compared to NOFILTER is zero.
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