ADO.NET and Database Interview questions

1. What is the role of the DataReader class in ADO.NET connections?

It returns a read-only, forward-only rowset from the data source. A DataReader provides fast access when a forward-only sequential read is needed.

2. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.

3. What is the wildcard character in SQL?

Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.

4. Explain ACID rule of thumb for transactions.

A transaction must be:
1. Atomic - it is one unit of work and does not dependent on previous and following transactions.
2. Consistent - data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t.
3. Isolated - no transaction sees the intermediate results of the current transaction).
4. Durable - the values persist if the data had been committed even if the system crashes right after.

5. What connections does Microsoft SQL Server support?

Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and password).

6. Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?

Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.

7. What does the Initial Catalog parameter define in the connection string?

The database name to connect to.

8. What does the Dispose method do with the Connection object?

Clears the unmanaged resources.

In addition to closing the connection, it also clears stateful nature of the SqlConnection instance.

9. What is a pre-requisite for connection pooling?

Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical

10. Difference between ADO.NET Dataset and an ADO Recordset?

ADO.NET DataSet: DIsconnected architechure . Maintainace relation schemas. MUtilple table grouping.
RecordSet: Connected one .


11. How can I execute a Transact SQL stored procedure (actually in the database) on a SQL 2000 database from an AS/400 CL program. ?

To execute either a DTS Package or a Stored Procedure, you have to set up a batch file on the server to call and it only has to have one record in it that is explained below.

The AS/400 command stays the same and is as follows:
RUNRMTCMD CMD('c:\TEST_BATCH) RMTLOCNAME('111.111.1.111' *IP) RMTUSER(*NONE)
The c:\TEST_BATCH is the batch file you need to set up.
Change the 111.111.1.111 to the IP address of the server to run it on.

To run a DTS package, the batch file will need to look like the following:
dtsrun /S "TESTSERVER" /U "TESTUSER" /P "TESTPWORD" /N "TEST_DTS"
Change TESTSERVER to the name of your server.
Change TERSUSER to a valid user id.
Change TESTPWORD to the password for the user.
Change TEST_DTS to the name of the DTS Package.
Pay attention to the case on the /S, /U, /P, and /N.
Make sure you save this as a .bat file not a .txt file.

To run a Stored Procedure, the batch file will need to look like the following:
osql -S "TESTSERVER" -d "TESTDB" -U "TESTUSER" -P "TESTPWORD" -q "exec dbo.TEST_STPROC"
Change TESTSERVER to the name of your server.
Change TESTUSER to a valid user id.
Change TESTPWORD to the password for the user.
Change dbo.TEST_STPROC to the name of the Stored Procedure.
Pay attention to the case on the –S, -d, -U, -P, and –q.
Make sure you save this as a .bat file not a .txt file.

12. How do I change the default location for database and log files during a SQL 2005 installation?

When you get to the list of services to install, click the Advanced button. Expand the SQL Server engine menu item, and select database files. Change the folder here. This will set the data file and log files to the same thing. You'll need to change the folder to different folders after the install is finished.