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The LA Fox Developer Newsletter
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March 2000
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Hot Tip...
Question: The following Select clause is taking 10 to 15 seconds to execute. The Rushmore optimization is always Partial. Why is it not Total?
SELECT RECNOO, DESCRIPTION, cargotype, commoditytype,; cubicfeet, grossweight, revenuetons,
wharfagechg;
FROM gltemDbf;
INTO ARRAY mResultArray;
WHERE
DOCUMENTNBR
==
‘123’ AND NOT DELETED()
Answer
First, you’ve used the
‘‘
operator, which is not Rushmoreoptimizable. If you need the sort of string comparison provided by
‘==‘,
you could use PADRO to pad the value being compared so that it is the same length as the field.
Second, SQL constructions for logicals do not follow the same rules as Xbase. You always need to include both sides of the expression; otherwise, the results can be unpredicatable. In Xbase, it is redundant to write something like:
IF DELETED()
=
.T.
since ‘IF DELETEDO’ is exactly the same. However, in SQL code, you should always write a WHERE clause like that. In your case, the WHERE should read:
WHERE DOCUMENTNBR
=
‘123’;
AND DELETEDO
=
.F.
ADO Jumpstart
(Con’t from page 6)
Underlying Value—I ndicates the current value in the data source. This property corresponds most closely to the CurVal(
)
function in Visual FoxPro. To populate the Value property of each Field object in the Fields collection, you need to invoke the Resync method of the Recordset object. With a client-side cursor, this property will return the same value as the OriginalValue property, since the recordset may or may not have an active connection.
Type—Indicates the data type of the Field object. The value of this property corresponds to a value contained in DataTypeEnum. Examples of values in DataTypeEnum are adBoolean, adlnteger, and adVarChar.
Defined Size—Specifies the size of the field containing a data element in the data source. For example, in SQL Server, the Country field in the Customers table of the Northwind database is 15 characters long. Therefore, the DefinedSize property of the Country Field object is 15.
(Con’t, page 9)
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(Microsoft has rearranged the MSDN website again, so many of the links we had have moved
-
and got longer!)
MSDN ON LINE:
There’s a ton of stuff here, look at the Magazines tab, and read some of the regular columns.
<msdn.microsoft.com>
MSDN Library
<msdn.microsoft.com/library>
Look in Technical Articles
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Visual Studio
I
Visual FoxPro
Three-Tier Apps:
MSDN Library: Building Three-Tier Client/Server Applications with Visual FoxPro
MTS: Microsoft Transaction Server
MSDN Library: Microsoft Transaction Server for Visual FoxPro
Developers
ODBC:
MSDN Library: Using Visual FoxPro to Access Remote Data
VS Installer:
MSDN Library:
Windows General
<www.winfiies.com>
XML
-
What’s New in XML for Microsoft Windows 2000
<msdn.microsoft. com/voices/xm!.asp>
[Ed. Note: Nick Nikula and Dan Covill have agreed to keep this list as a permanent item in the Tips letter. Contributions solicited. Visit the website at
http://www.elsoftware.com/J
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