Data Management - Applications - C170 2023/24

Key they are used to ensure that each row in a table is uniquely identifiable. They are also used to establish relationships among tables and to ensure the integrity of the data. A key consists of one or more attributes that determine other attributes. For example, an invoice number identifies all of the invoice attributes, such as the invoice date and the customer name. Determination the state in which knowing the value of one attribute makes it possible to determine the value of another. functional dependence relationships based on determination. which means that the value of one or more attributes determines the value of one or more other attributes. The standard notation for representing the relationship between STU_NUM and STU_LNAME is as follows: STU_NUM -- STU_LNAME determinant is the attribute whose value determines another is called the determinant or the key. dependent. The attribute whose value is determined by the other attribute is called the dependent. Composite Entity (bridge entity) An entity designed to transform an M:N relationship into two 1:M relationships. Cardinality denotes how many instances of one object are related to instances of another object. Example: One order can be assigned to only one customer but a customer can have multiple orders (one-to-many relationship). Cardinality can be shown in crow's feet notations, utilizing a straight line for 1 and a crow's foot for many. cardinality refers to the maximum number of times this relationship may occur Modality denotes an instance of a specific entity is optional or mandatory in a relationship. For instance an open order must have a customer associated with it, but every customer does not need to have an open order. Modality is expressed with a straight line for modality 1 or a circle for modality 0. These are drawn in the relationship inside of the cardinality symbols modality refers to the minimum number of times an instance of an entity can be associated with an instance in a related table space In a DBMS, a logical storage space used to group related data. Also known as a file group. access plan A set of instructions generated at application compilation time that is created and managed by a DBMS. The access plan predetermines how an application's query will access the database at run time. algorithm a process or set of operations in a calculation