Data Management for Programmers

What is a base relation?

A base relation is a named relation corresponding to an entity in the conceptual schema whose tuples are physically stored in the database.

What is a candidate key?

A candidate key is a superkey such that no proper subset is a superkey within the relation.

What is a conceptual data model?

A conceptual data model represents the logical of community view that is DBMS independent.

What is a DML (Data Manipulation Language)?

A data manipulation language is a language that provides a set of operations to support the basic data manipulation operations on the data held in the database. This usually involves inserting, modifying, retrieval, and deletion of data.

What is a data model?

A data model is an integrated collection of concepts for describing and manipulating data, relationships between data, and constraints on the data in an organization.

What is the data in a database at any particular point?

A database instance is the data in the database at any particular point.

What is a database schema?

A database schema is the overall description of the database.

What is a disjoint constraint?

A disjoint constraint describes the relationship between members of the subclasses and indicates whether it is possible for a member of a superclass to be a member of one or more than one subclass.

What is a domain?

A domain is the set of allowable values for one or more attributes.

What is a foreign key?

A foreign key is an attribute, or set of attributes, within one relations that matches the candidate key of some relation.

What is a multilevel relation?

A multilevel relation is a relation that reveals different tuples to users with different security clearances.

What is a participation constraint?

A participation constraint determines whether every member in the superclass must participate as a member of a subclass.

What is a privilege?

A privilege allows a user to create or access (read, write, or modify) some database object. Granting too many privileges can be a threat to security.

What is a query language?

A query language can be defined as a high level special purpose language used to satisfy diverse requests for the retrieval of data held in the database.

What is a relation?

A relation is a table with columns and rows.

What is a relational database?

A relational database is a collection of normalized relations with distinct relations names.

What is a relationship?

A relationship is an association between entities.

What is a report generator?

A report generator is a facility for creating reports from data stored in the database. It provides much greater control over what the output looks like.

What is a schema?

A schema is a system view of a database.

What is a shared subclass?

A shared subclass is a subclass with more than one superclass. It inherits attributes from all of its superclasses.

What is a subclass?

A subclass is a distinct subgrouping of occurrences of an entity type which must be represented in a data model. For example, manager, secretary, etc. could all be subclasses of staff.

What is a subschema?

A subschema is a user view of a database.

What is a superclass?

A superclass is an entity type that includes one or more distinct subgroupings of its occurrences which must be represented in a data model.

What is a superkey?

A superkey is an attribute, or set of attributes, that uniquely identifies a tuple within a relation.

What is a tuple?

A tuple is a row of a relation.

What is a view?

A view is the dynamic result of one or more relational operations operating on the base relations to produce another relation. A view is a virtual relation that does not necessarily exist in the database but can be produced upon request by a particular user at the time of request.

What are alternate keys?

Alternate keys are candidate keys that were not chosen to be the primary key.

What is an attribute in regards to a relation?

An attribute is a named column of a relation.

What is an attribute?

An attribute is a property that describes some aspect of the object that we wish to record.

What is an entity?

An entity is a distinct object (person, place, thing, concept, or event) in the organization that is to be represented in the database.

What is an information system?

An information system is the resources that enable the collection, management, control, and dissemination of information throughout and organization.

What is an internal data model?

An internal data model represents the conceptual schema in such a way that it can be understood by the DBMS.

What is attribute inheritance?

Attribute inheritance is when a subclass inherits attributes of the superclass.

What is cardinality?

Cardinality of a relation is the number of tuples it contains.

What is data independence?

Data independence means that the upper levels of the database are not changed by changes to the lower levels of the database. There are two kinds of data independence: logical and physical.

What is database administration?

Database administration is the management of the physical realization of a database system. This includes the physical design and implementation, setting security and integrity controls, monitoring system performance, and reorganizing the database.

What is database planning?

Database planning is the start of the database system development lifecycle.

What is database security?

Database security is the mechanisms that protect the database against intentional or accidental threats.

What is discretionary access control?

Discretionary Access Control (or DAC) provides GRANT and REVOKE commands that can give or take away privileges from users. This is usually found in commercial DBMSs.

What is encryption?

Encryption is the encoding of the data by a special algorithm that renders the data unreadable by any program without the decryption key.

What is entity integrity?

Entity integrity is when no attribute of a primary key can be null.

What is generalization?

Generalization is the process of minimizing the differences between entities by identifying their common characteristics.

What does it mean if the subclasses are disjoint?

If the subclasses are disjoint then an entity occurrence can be a member of only one of those subclasses.

What is Kerberos?

Kerberos is a server of secured user names and passwords.

What is logical data independence?

Logical data independence is the immunity of the external schema to changes in the conceptual schema.

What is Mandatory Access Control?

Mandatory Access Control (or MAC) is based on system-wide policies that cannot be changed by individual users.

What is physical data independence?

Physical data independence is the immunity of the conceptual schema to changes in the internal schema.

What is referential integrity?

Referential integrity is when a foreign key exists in a relation and the foreign key value must match a candidate key value of some tuple in its home relation or the foreign key value must be wholly null.

What is required data?

Required data is data that must contain a valid value. They cannot contain a null value.

What is specialization?

Specialization is the process of maximizing the differences between members of an entity by identifying their distinguishing characteristics.

What is splitting the database?

Splitting the database is a way to protect data in a database by storing the database tables separately.

What is responsible for the mapping between the different type s of schemas?

The DBMS is responsible for mapping between the three types of schemas.

What is the conceptual level of the ANSI-SPARC architecture?

The conceptual level of the ANSI-SPARC architecture provides both the mapping and the desired independence between the external and internal levels. This level describes what data is stored in the database and the relationships among the stored data.

What does the conceptual schema describe?

The conceptual schema describes all the entities, attributes, and relationships together with integrity constraints.

What is the data dictionary?

The data dictionary is used to describe the system catalog.

What is a degree of a relation?

The degree of a relation is the number of attributes it contains.

What is the ER model?

The entity relationship model (or ER model) is one of the main techniques for database design.

What is the external level of the ANSI-SPARC architecture?

The external level of the ANSI-SPARC architecture is the way the user's perceive the data. These are the views of the data that the users see.

What does the external schema (subschema) describe?

The external schema (or subschema) describes the different views of the data. Multiple external subschemas exist.

What is the internal level of the ANSI-SPARC architecture?

The internal level of the ANSI-SPARC architecture is the physical representation of the database on the computer that is this level describes how the data is stored in the database. It is concerned with storage space allocation for data and indexes, record descriptions for storage, record placement, and data compression and data encryption.

What does the internal schema describe?

The internal schema is a complete description of the internal model containing the definitions of stored records, the methods of representation, the data fields, and the indexes and storage structures used.

What is the manipulative part of the data model?

The manipulative part of the data model defines the types of operations that are allowed on the data. This includes operations for updating or retrieving data from the database and for changing the structure of the database.

What is the physical level?

The physical level exists below the internal level, but it isn't very clear what functions it performs as it varies widely depending on the DBMS that is being used. It consists of items only the operating system knows such as if records are stored in contiguous bytes on the disk.

What is a primary key?

The primary key is a candidate key that is selected to identify tuples uniquely within the relation.

What is a set of integrity constraints of the data model?

The set of integrity constraints of the data model ensures that the data is accurate.

What is the structural part of the data model?

The structural part of the data model is a set of rules according to which databases can be constructed.

What is the system catalog?

The system catalog is the place where the tables are stored.

What are the three components of the data model?

The three components of the data model are the structural part, the manipulative part, and a set of integrity constraints.

What are the three levels of the ANSI-SPARC architecture?

The three levels of the ANSI-SPARC architecture are the external, conceptual, and internal levels.

What is the universe of discourse?

The universe of discourse (an external data model) represents each user's view of the organization.

What is a DDL (Data Definition Language)?

a data definition language allows the DBA or user to describe and name entities, attributes, and relationships required for each application together with any associated integrity and security constraints. This creates the layout of the database such as tables.