Greetings,
I have read initial requirements and let me assure you that our .NET team is VERY strong, as we have done few very bigger and complex Applications, so technically you won't have any issues.
Here's answer to all your questions, even though they are very basic questions we ask employees in their interview to hire :), I cannot answer in detail, because there are character limitations in this initial message board:
1) How would you establish a many-to-many relationship in a database.
LEADconcept: A many-to-many relationship refers to a relationship between tables in a database when a parent row in one table contains several child rows in the second table, and vice versa.
2) What are indexes,? what is the diff between clustered-index and non-clustered index.
LEADconcept: An index can be created in a table to find data more quickly and efficiently. A clustered index actually describes the order in which records are physically stored on the disk, hence the reason you can only have one. A Non-Clustered Index defines a logical order that does not match the physical order on disk.
3) How can you improve query performance?
LEADconcept: There are many ways to improve the query performance, i.e .Re-writing SQL Query, Avoid Multiple Joins in a Single Query, Eliminate Cursors from the Query, Avoid Use of Non-correlated Scalar Sub Query, Drop Unused Indexes, using joins instead of subqueries etc.