MIS 325 Lecture Notes - Lecture 10: Superkey, Compound Key, Relational Model

• School: UT-Austin
• Department: Management Information Systems
• Course: MIS 325
• Professor: John Mote

Document Summary

The composite entity"s primary key comprises at least the primary keys of the entities that it connects. composite key - a multiple-attribute key. data dictionary - a dbms component that stores metadata data about data. Thus, the data dictionary contains the data definition as well as their characteristics and relationships. A data dictionary may also include data that are external to the dbms. The relationship b is dependent on a is equivalent to a determines b, and is written as ab. homonym - the use of the same name to label different attributes. Some relational software automatically checks for homonyms and either alerts the user to their existence or automatically makes the appropriate adjustments. index - an ordered array of index key values and row id values. Indexes are generally used to speed up and facilitate data retrieval. inner join - a join operation in which only rows that meet a given criterion are selected.