Question

I’m trying to read data in Visual Studio from multiple tables.

How do you read data from different tables? Do I have to create

• a separate connection,
• a separate command,
• a separate DataReader for each SELECT?

Thank you in advance!

Answer 1

If the tables have a link then you JOIN them in the database engine first.

SELECT
   O.Col1, C.Col2, ...
FROM
   Orders O
   JOIN
   Customers C ON O.CustomerID = C.Customer
WHERE
    ...

If they are not to be JOINed, you can issue multiple SELECTs in one call and iterate through several DataReaders. Or load a DataSet via a DataAdaptor