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multiple data sets

Posted on 2005-04-21
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Last Modified: 2010-04-23
Hi
Another one for you...
As i understand there are four main objects needed to connect to a DB
Connection
Command
DataAdapter
DataSet

which of these can be reused across all queries and resulting datasets and which do i need to create for each separate SQL query

I had assumed that i only needed to do the connection once -but it only works with multiple connections... so does this mean that for every connection i make to the DB i need to go through setting up and populating each of these objects? isn't that really inefficient? it certainly seems it from the amount of code i am going to have to generate...

any tips or comments - am i going about this completely the wrong way?

thanks
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Question by:lz7cjc
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RonaldBiemans earned 200 total points
ID: 13832473
you need just one connection per database.
if you have multiple tables you want to update, create a dataadapter for each table.
if you don't want to update the table you could reuse the same dataadapter
the same goes for commands.
only one dataset is usually needed. the data inside the dataset are updated by the indivual adapters.

if you want to return just 1 value from a table, use the executescalar command
if you want to execute a query than doesn't return anything use executenonquery,

there is also the datareader

use this if the result doesn't need to be updated and you just want to loop through a set of variables

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by:lz7cjc
ID: 13832506
thanks Ronald... so why, when i reused the same DB connection, did i get an error?

would it be possible to explain a little more simply, how i can reuse a dataadapter on the same page... surely if i need to reference the data adapter to display one set of records it is in use and can't be used for another purpose... i.e aren't the commands executed in a linear fashion?

perhaps some example code of how i would connect once to the database to access 2 different datasets and then display the results, would help with my confusion? (lets forget about update etc for the moment and assume i am just displaying... i can ask a separate question on that later if i need to)

thanks
Nick
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by:RonaldBiemans
ID: 13832541
Is this for web or windows ?
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Author Comment

by:lz7cjc
ID: 13832788
it is for web... all these questions relate to web

i am going to award the points on this since as it seems to have converged with my other question... count it as a downpayment!
thanks
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