C170 - Applications - Data Management Questions and Answers Graded A+

C170 - Applications - Data Management Questions and Answers Graded A+ FROM Clause that specifies the table or tables from which data is to be retrieved. Table Row Also called a tuple; represents a single entity occurrence within the entity set Brainpower Read More Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:08 / 0:15 Full screen Table Column Has a distinct name and represents an attribute Superkey An attribute or combination of attributes that uniquely identifies each row in a table Candidate key A minimal superkey A key that does not contain a subset of attributes that is itself a superkey Based on a full functional dependency Primary Key A candidate key selected to uniquely identify all other attribute values in any given row; cannot contain null entries Foreign Key An attribute or combination of attributes in one table whose values must either match the primary key in another table or be null Secondary Key An attribute or combination of attributes used strictly for data retrieval purposes Inner Join A join operation in which only rows that meet a given criterion are selected It is the most commonly used type of join. Only RETURNS MATCHED RECORDS from the tables that are being joined Right Outer Join Returns all rows from the right table, and the matched rows from the left table. The result is NULL in the left side when there is no match. Full Join Returns all rows from the left table and from the right table. It combines the output of both left and right joins. Theta Join Links tables using an inequality comparison operator It is considered to be an extension of natural join. Natural Join Yields a new table composed of ONLY THE ROWS WITH COMMON VALUES in their common attributes. It is a three-stage process. Relational Select operation Retrieves one or more rows of a table, depending on whether the search argument is a unique or non-unique attribute. Relational Project operation Retrieves all rows and some attributes of a table without using a WHERE clause to limit which rows of the table are included Join operation Integrates data from two or more tables or combines them. A join operation can be implemented in the FROM and WHERE clauses Entity integrity Describes a condition in which all tuples within a table are uniquely identified by their primary key Referential integrity Describes a condition in which a foreign key value has a match in the corresponding table or in which the foreign key value is null Composite Entity An entity designed to transform an M:N relationship into two 1:M relationships. This entity's primary key comprises at least the primary keys of the entities that it connects. Also known as a bridge entity or associative entity. Join The real power behind the relational database, allowing the use of independent tables linked by common attributes. Codd's Nonsubversion Rule of Relational Databases If the system supports low level access to the data, users must not be allowed to bypass the integrity rules of the database PROJECT operation Returns only the attributes requested, in the order in which they are requested. Generalization Hierarchies Implemented as 1:1 relationships DIVIDE operation Uses one single column table (e.g., column "a") as the divisor and one two column table (e.g., columns "a" and "b") as the dividend Fully Functional Dependency When an attribute is functionally dependent on a composite key, but not on any subset of that composite key Secondary key A key that is used strictly for data retrieval purposes Flags Special codes used by designers to indicate the absence of some value 1:1 Relationship Should be rare in database design NOT NULL constraint Placed on a column to ensure that every row in the table has a value for that column Keys Used to establish relationships among tables and to ensure the integrity of the data. Predicate Logic Provides a framework in which an assertion (statement of fact) can be verified as either true or false. Data Dictionary Contains at least all of the attribute names and characteristics for each table in the system Provides a detailed description of all tables found within the user/designer-created database. Union-Compatible When two or more tables share the same number of columns, and when their corresponding columns share the same or compatible domains DATE attribute Contain calendar dates stored in a special format known as the Julian date format How a Null is created By pressing the Enter key or the Tab key to move to the next entry without making a prior entry of any kind Closure A property of relational operators that permits the use of relational algebra operators on existing tables (relations) to produce new relations.