DAD 220 Chapter 2: Relational Databases Exam Questions And Correct Answers All 100% Verified

DAD 220 Chapter 2: Relational Databases Exam Questions And Correct Answers All 100% Verified relational model - Answer -A database model based on mathematical principles, with three parts: 1. A data structure that prescribes how data is organized. 2. Operations that manipulate data structures. 3. Rules that govern valid relational data. set - Answer -a collection of values, or elements, with no inherent order Three mathematical concepts the relational data structure is based on: - Answer -1. A domain is a named set of possible database values, such as integers, dictionary words, or logical values TRUE and FALSE. 2. A tuple is a finite sequence of values, each drawn from a fixed domain. Ex: (3, apple, TRUE) is a tuple drawn from domains (Integers, DictionaryWords, LogicalValues). 3. A relation is a named set of tuples, all drawn from the same sequence of domains. Ex: The relation below is named Grocery and contains three tuples. attribute - Answer -In the relational model, each tuple position is called a/an ____________ and given a unique name. relational algebra - Answer --Union — combines two tables with identical columns into one table. -Difference — removes all rows of one table from another table. -Projection — eliminates one or more columns of a table. -Selection — selects a subset of rows of a table. -Join — combines two tables with different columns into one table. -Product — lists all possible combinations of rows of two tables. Relational rules aka integrity rules - Answer -logical constraints that ensure data is valid and conforms to business policy Structural rules - Answer -relational rules that govern data in every relational database Examples: -Unique primary key — all tables should have a column with no repeated values, called the primary key and used to identify individual rows. -Unique column names — different columns of the same table must have different names. -No duplicate rows — no two rows of the same table may have identical values in all columns.