Database Management Systems

An alternate key is any attribute that can uniquely identify an entity instance, other than the primary key. It provides an alternative way to access records and must have the uniqueness property of a key, even though it's not designated as the primary identifier.

The parent entity Company has three child entities: Employee, Product, and Order. In a relational model, each child entity must contain the parent's primary key as a foreign key to establish the relationship. Therefore company_id appears once in each of the three child entities, totaling three appearances in the model.

When a parent entity's key becomes part of the child entity's primary key, it creates an identifying relationship. The child entity cannot exist without the parent because its identity depends on the parent's key. In contrast, a non-identifying relationship would have the foreign key as a non-key attribute.

Metadata is defined as data about data that describes other data structures (like a data dictionary) and is self-describing. It does not include actual user or operational data itself, making that choice the correct non-characteristic.

A mandatory one-to-one relationship between two entities often indicates they should be combined into a single entity. If they truly must be separate, the mandatory one-to-one constraint suggests the model is missing attributes - there should be additional distinguishing characteristics to justify their separation.

A schema is a structural representation of a database or data model, expressed either graphically (as diagrams) or through a definition language. It defines the organization of data, including tables, attributes, relationships, and constraints. It is not a schedule, flow diagram, or action plan.

In entity-relationship modeling, an entity (like Book) has properties that describe it. These properties are called attributes. Title, Author First Name, Author Last Name, Book Genre, and Date Published are all attributes of the Book entity. An attribute is a characteristic or property of an entity.

In a many-to-many relationship between students and classes, a junction table (associative entity) is needed. This table contains foreign keys from both entities. The composite key is the combination of both identifying attributes - in this case, the student's name and the class name together uniquely identify each enrollment record.

SAS is a comprehensive software suite designed for data access (retrieving data from multiple sources), data management (cleansing and transforming data), and data analysis (performing statistical analysis and reporting). Because it covers all these functions, the option selecting all three is correct.

sp_who2 is a system stored procedure that returns information about current users, sessions, and processes in SQL Server. The query 'select * from sys.sysprocesses' directly accesses the system view containing process information. sp_helpdb shows database information, and sp_helpprocess is not a valid SQL Server stored procedure. Both C and D are valid methods.

SQL Server's default port for TCP/IP communication is 1433. This is the well-known port used by the SQL Server Database Engine to listen for incoming client connections. Port 1434 is used for the SQL Server Browser Service (which helps clients find named instances), while 1432 and 1435 are not standard SQL Server ports.

Database mirroring requires the FULL recovery model because it needs to maintain a complete transaction log to ship log records from the principal to the mirror server. The Simple recovery model truncates the log automatically, preventing log shipping. Bulk-logged recovery also has limitations that make it unsuitable for mirroring. 'Half' is not a valid recovery model in SQL Server.

SQL Server supports two authentication modes: Windows Authentication (uses Windows Active Directory accounts) and Mixed Mode (allows both Windows Authentication and SQL Server authentication). 'Builtin/Administrator' is not a mode name. 'SQL authentication' alone refers to the SQL Server-specific authentication used within Mixed mode, not a standalone mode.

In SQL Server, transaction logs are truncated by backing them up (BACKUP LOG). This marks the inactive portion of the log as truncatable and reuses the space. Simply firing a TRUNCATE command doesn't work on transaction logs. The database must be in Full or Bulk-Logged recovery model for log backups to be meaningful. Logs CAN be truncated in SQL Server - this is what backup and maintenance plans do.

SQL Server has 5 system databases: Master (stores system-level information), Model (template database), MSDB (stores SQL Agent jobs, alerts, and operators), TempDB (temporary workspace), and Resource (read-only system objects). MSDB specifically stores information about scheduled jobs running on SQL Server. The correct answer is '5,MSDB'.