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Base de données, Tables, Vues, Index et syntaxe SQL
>I have a VFP 6 file-server app that uses parameterized local views to access VFP tables. The EXE resides on a workstation and the DBFs reside on a server. I'm trying to troubleshoot some performance problems. I have some questions.
>1. When I issue the USE command to open my parameterized view, exactly what portion of the table/index is transferred over the network from the server to the workstation?
if you have nodata set then only the header information is send.
>2. When I issue a requery() after changing my view's parameter, does the entire table transfer from the server to the workstation, or just the one record I'm requesting? I would think that since this app is not client-server, the entire table would have to transfer each time.
VFP uses rushmore to minimise the amount of data that needs to be moved around.
So parts of the cdx or all in some cases and only the records in your resultd set actually get transfered across the network.
>3. When I issue a tableupdate(), does the entire table transfer back to the server or just the records that I have updated? Since there is no intelligent app on the server, how does VFP manage this update?
VFP internally treats the file as a dbf and processes it pretty much the same way it would if you had opened the table itself.
Frankly there is no real advantage to using view for you application in terms of network I/O ... UNLESS you move to a SQL back end ... MSDE would be a good choice in such a case.
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