Where do you think the users names and passwords will be stored in sql server?

They get stored in master db in the sysxlogins table.

What is a deadlock?

Deadlock is a situation when two processes, each having a lock on one piece of data, attempt to acquire a lock on the other's piece. Each process would wait indefinitely for the other to release the lock, unless one of the user processes is terminated. 
SQL Server detects deadlocks and terminates one user's process

What is ACID?

ACID (an acronymn for Atomicity Consistency Isolation Durability) is a concept that Database Professionals generally look for when evaluating databases and application architectures. For a reliable database all this four attributes should be achieved. 

Atomicity is an all-or-none proposition. 

Consistency guarantees that a transaction never leaves your database in a half-finished state. 

Isolation keeps transactions separated from each other until they're finished. 

Durability guarantees that the database will keep track of pending changes in such a way that the server can recover from an abnormal termination. 

Above four rules are very important for any developers dealing with databases

What Is DTS?

DTS is a set of tools you can use to import, export, and transform heterogeneous data between one or more data sources, such as Microsoft SQL Server, Microsoft Excel, or Microsoft Access. Connectivity is provided through OLE DB, an open-standard for data access. ODBC (Open Database Connectivity) data sources are supported through the OLE DB Provider for ODBC.

What is Log Shipping?

In Microsoft SQL Server, you can use log shipping to feed transaction logs from one database to another on a constant basis. Continually backing up the transaction logs from a source database and then copying and restoring the logs to a destination database keeps the destination database synchronized with the source database. This allows you to have a backup server and also provides a way to offload query processing from the main computer (the source server) to read-only destination servers.

What are sequence diagrams? What you will get out of this sequence diagrams?

Sequence diagrams document the interactions between classes to achieve a result, such as a use case. Because UML is designed for object-oriented programming, these communications between classes are known as messages. The sequence diagram lists objects horizontally, and time vertically, and models these messages over time.

What is a tuple?

A tuple is an instance of data within a relational database.

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