{"id":44,"date":"2013-12-12T00:09:53","date_gmt":"2013-12-12T00:09:53","guid":{"rendered":"http:\/\/opentextbc.ca\/dbdesign01\/?post_type=chapter&#038;p=44"},"modified":"2022-01-28T01:01:15","modified_gmt":"2022-01-28T01:01:15","slug":"chapter-7-the-relational-data-model","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/dbdesign01\/chapter\/chapter-7-the-relational-data-model\/","title":{"raw":"Chapter 7 The Relational Data Model","rendered":"Chapter 7 The Relational Data Model"},"content":{"raw":"The relational data model was introduced by E. F. Codd in 1970. Currently, it is the most widely used data model.\r\n\r\nThe relational model has provided the basis for:\r\n<ul>\r\n \t<li>Research on the theory of data\/relationship\/constraint<\/li>\r\n \t<li>Numerous database design methodologies<\/li>\r\n \t<li>The standard database access language called s<em>tructured query language (SQL)<\/em><\/li>\r\n \t<li>Almost all modern commercial database management systems<\/li>\r\n<\/ul>\r\nThe relational data model describes the world as \"a collection of inter-related relations (or tables).\"\r\n<h2>Fundamental Concepts in the Relational Data Model<\/h2>\r\n<h3>Relation<\/h3>\r\nA\u00a0<em>relation,\u00a0<\/em>also known as a <em>table<\/em> or <em>file<\/em>,\u00a0is a subset of the Cartesian product of a list of domains characterized by a name.\u00a0And within\u00a0a table, each row represents a group of related data values. A <em>row<\/em>, or record, is also known as a <em>tuple<\/em>. The columns in a table is a field and is also referred to as an attribute. You can also think of it this way: an attribute is used to define the record and a record contains a set of attributes.\r\n\r\nThe steps below outline the logic between a relation and its domains.\r\n<ol>\r\n \t<li>Given<em>\u00a0n<\/em>\u00a0domains\u00a0are\u00a0denoted by D1, D2, \u2026 Dn<\/li>\r\n \t<li>And<em>\u00a0r<\/em>\u00a0is a relation defined on these domains<\/li>\r\n \t<li>Then\u00a0\u00a0r \u2286 D1\u00d7D2\u00d7\u2026\u00d7Dn<\/li>\r\n<\/ol>\r\n<h3>Table<\/h3>\r\nA database is composed of multiple tables and each<em>\u00a0<\/em>table holds the data. Figure 7.1 shows a database that contains three tables.\r\n\r\n[caption id=\"attachment_29\" align=\"aligncenter\" width=\"300\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Banking-Systems-RDBMS-300x195.jpg\"><img class=\"wp-image-29\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/School-Database-Fig-1-300x221.jpg\" alt=\"Blue cylinder with three white rectangles each with a list of words.\" width=\"300\" height=\"221\" \/><\/a> Figure 7.1. Database with three tables.[\/caption]\r\n<h3>Column<\/h3>\r\nA database stores pieces of information or facts in an organized way. Understanding how to use and get the most out of databases requires us to understand that method of organization.\r\n\r\nThe principal storage units are called <em>columns<\/em>\u00a0or <em>fields<\/em>\u00a0or <em>attributes<\/em>. These house the basic components of data into which\u00a0your content can be broken down. When deciding which fields to create, you need to think generically about your information, for example, drawing out the common components of the information that you will store in the database and avoiding the specifics that distinguish one item from another.\r\n\r\nLook at the example of an ID card in Figure 7.2 to see the relationship between fields and their data.\r\n\r\n[caption id=\"attachment_41\" align=\"aligncenter\" width=\"300\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177.jpg\"><img class=\"wp-image-41 size-full\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177.jpg\" alt=\"Record-300x177\" width=\"300\" height=\"177\" \/><\/a> Figure 7.2. Example of an ID card by A. Watt.[\/caption]\r\n<h3>Domain<\/h3>\r\nA <em>domain<\/em> is the original sets of atomic values used to model data. By <em>atomic value<\/em>, we mean that each value in the domain is indivisible as far as the relational model is concerned. For example:\r\n<ul>\r\n \t<li>The domain of Marital Status has a set of possibilities:\u00a0Married, Single, Divorced.<\/li>\r\n \t<li>The domain of Shift has the set of all possible days: {Mon, Tue, Wed\u2026}.<\/li>\r\n \t<li>The domain of Salary is the set of all floating-point numbers greater than 0 and less than 200,000.<\/li>\r\n \t<li>The domain of First Name is the set of character strings that represents names of people.<\/li>\r\n<\/ul>\r\nIn summary, a domain is a set of acceptable values that a column is allowed to contain. This is based on various properties and the data type for the column. We will discuss data types in another chapter.\r\n<h3>Records<\/h3>\r\nJust as the content of any one document or item needs to be broken down into its constituent bits of data for storage in the fields, the link between them also needs to be available so that they can be reconstituted into their whole form. Records allow us to do this. <em>Records<\/em> contain fields that are related, such as a customer or an employee. As noted earlier, a tuple is another term used for record.\r\n\r\nRecords and fields form the basis of all databases. A simple table \u00a0gives us the clearest picture of how records and fields work together in a\u00a0database storage project.\r\n\r\n[caption id=\"attachment_136\" align=\"aligncenter\" width=\"300\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/RDBMS-300x2091.jpg\"><img class=\"wp-image-136\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Table-Description-300x146.jpg\" width=\"300\" height=\"146\" \/><\/a> Figure 7.3. Example of a simple table by A. Watt.[\/caption]\r\n\r\nThe<span style=\"color: #333333;\"> simple table<\/span> example in Figure 7.3 shows us how fields can hold a range of different sorts of data. This one has:\r\n<ul>\r\n \t<li>A Record ID field: this is an ordinal number; its data type is an integer.<\/li>\r\n \t<li>A PubDate field: this is displayed as day\/month\/year; its data type is date.<\/li>\r\n \t<li>An Author field: this is displayed as\u00a0Initial. Surname; its data type is text.<\/li>\r\n \t<li>A Title field text: free text can be entered here.<\/li>\r\n<\/ul>\r\nYou can command the database to sift through its data and organize it in a particular way. For example, you can request that a selection of records be limited by date: 1. all before a given date, 2. all after a given date or 3. all between two given dates. Similarly, you can choose to have records sorted by date. Because the field, or record, containing the data is set up as a Date field, the database reads the information in the Date field not just as numbers separated by slashes, but rather, as dates that\u00a0must be ordered according to a calendar system.\r\n<h3>Degree<\/h3>\r\nThe <em>degree<\/em> is the number of attributes in a table. In our example in Figure 7.3, the degree is 4.\r\n<h2>Properties of a Table<\/h2>\r\n<ul>\r\n \t<li>A table has a name that is distinct from all other tables in the database.<\/li>\r\n \t<li>There are no duplicate rows; each row is distinct.<\/li>\r\n \t<li>Entries in columns are atomic. The table<span style=\"color: #333333;\">\u00a0does\u00a0<\/span>not contain repeating groups or multivalued attributes.<\/li>\r\n \t<li>Entries from columns are from the same domain based on their data type including:\r\n<ul>\r\n \t<li>number (numeric, integer, float, smallint,\u2026)<\/li>\r\n \t<li>character (string)<\/li>\r\n \t<li>date<\/li>\r\n \t<li>logical (true or false)<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Operations combining different data types are disallowed.<\/li>\r\n \t<li>Each attribute has a distinct name.<\/li>\r\n \t<li>The sequence of columns is insignificant.<\/li>\r\n \t<li>The sequence of rows is insignificant.<\/li>\r\n<\/ul>\r\n&nbsp;\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Key Terms<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\n<strong>atomic value<\/strong>:\u00a0each value in the domain is indivisible as far as the relational model is concerned<strong>attribute<\/strong>:\u00a0principle storage unit in a database\r\n\r\n<strong>column: <\/strong>see <em>attribute<\/em>\r\n\r\n<strong>degree<\/strong>: number of attributes in a table\r\n\r\n<strong>domain<\/strong>:\u00a0the original sets of atomic values used to model data;\u00a0a set of acceptable values that a column is allowed to contain\r\n\r\n<strong>field<\/strong>:\u00a0see\u00a0<em>attribute<\/em>\r\n\r\n<strong>file<\/strong>:see<em> relation<\/em>\r\n\r\n<strong>record<\/strong>:\u00a0contains fields that are related; <em>see tuple<\/em>\r\n\r\n<strong>relation<\/strong>: a\u00a0subset of the Cartesian product of a list of domains characterized by a name; the technical term for table or file\r\n\r\n<strong>row<\/strong>: <em>see tuple<\/em>\r\n\r\n<strong>structured query language (SQL)<\/strong>: the standard database access language\r\n\r\n<strong>table:<\/strong>see<em> relation<\/em>\r\n\r\n<strong>tuple<\/strong>:\u00a0a technical term for row or record\r\n<h4>Terminology Key<\/h4>\r\nSeveral of the terms used in this chapter are synonymous. In addition to the Key Terms above, please refer to Table 7.1 below. The terms in the Alternative 1 column are most commonly used.\r\n\r\n[caption id=\"attachment_43\" align=\"alignnone\" width=\"288\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms.jpg\"><img class=\"wp-image-43 size-full\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms.jpg\" alt=\"A database table with words.\" width=\"288\" height=\"110\" \/><\/a> Table 7.1. Terms and their synonyms by A. Watt.[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Exercises<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\n<em> Use Table 7.2 to answer questions 1-4.<\/em>\r\n<ol>\r\n \t<li>Using correct terminology, identify and describe all the components \u00a0in Table 7.2.<\/li>\r\n \t<li>What is the possible domain for field EmpJobCode?<\/li>\r\n \t<li>How many records are shown?<\/li>\r\n \t<li>How many attributes are shown?<\/li>\r\n \t<li>List the properties of a table.<\/li>\r\n<\/ol>\r\n[caption id=\"attachment_249\" align=\"aligncenter\" width=\"600\"]<a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554.jpg\"><img class=\"wp-image-249\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554.jpg\" alt=\"Table with 5 columns and 5 rows.\" width=\"600\" height=\"112\" \/><\/a> Table 7.2. Table for exercise questions, by A. Watt.[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<h2>\u00a0Attribution<\/h2>\r\n<span style=\"color: #1f1f1d;\">This chapter of\u00a0<\/span><em style=\"color: #1f1f1d;\">Database Design<\/em><span style=\"color: #1f1f1d;\"> (including images, except as otherwise noted) is a derivative copy of\u00a0<a href=\"http:\/\/cnx.org\/contents\/e5ac0441-0e54-4895-9112-fb3a4ee9bce1@1\">Relational Design Theory<\/a><\/span><span style=\"color: #1f1f1d;\">\u00a0by<\/span>\u00a0Nguyen Kim Anh<span style=\"color: #1f1f1d;\">\u00a0licensed under\u00a0<\/span><a style=\"color: #870d0d;\" href=\"http:\/\/creativecommons.org\/licenses\/by\/3.0\/\">Creative Commons Attribution License 3.0 license<\/a>\r\n\r\nThe following material was written by Adrienne Watt:\r\n<ol>\r\n \t<li>All or part of the sections on relations, tables, columns and degree<\/li>\r\n \t<li>Key Terms<\/li>\r\n \t<li>Exercises<\/li>\r\n<\/ol>","rendered":"<p>The relational data model was introduced by E. F. Codd in 1970. Currently, it is the most widely used data model.<\/p>\n<p>The relational model has provided the basis for:<\/p>\n<ul>\n<li>Research on the theory of data\/relationship\/constraint<\/li>\n<li>Numerous database design methodologies<\/li>\n<li>The standard database access language called s<em>tructured query language (SQL)<\/em><\/li>\n<li>Almost all modern commercial database management systems<\/li>\n<\/ul>\n<p>The relational data model describes the world as &#8220;a collection of inter-related relations (or tables).&#8221;<\/p>\n<h2>Fundamental Concepts in the Relational Data Model<\/h2>\n<h3>Relation<\/h3>\n<p>A\u00a0<em>relation,\u00a0<\/em>also known as a <em>table<\/em> or <em>file<\/em>,\u00a0is a subset of the Cartesian product of a list of domains characterized by a name.\u00a0And within\u00a0a table, each row represents a group of related data values. A <em>row<\/em>, or record, is also known as a <em>tuple<\/em>. The columns in a table is a field and is also referred to as an attribute. You can also think of it this way: an attribute is used to define the record and a record contains a set of attributes.<\/p>\n<p>The steps below outline the logic between a relation and its domains.<\/p>\n<ol>\n<li>Given<em>\u00a0n<\/em>\u00a0domains\u00a0are\u00a0denoted by D1, D2, \u2026 Dn<\/li>\n<li>And<em>\u00a0r<\/em>\u00a0is a relation defined on these domains<\/li>\n<li>Then\u00a0\u00a0r \u2286 D1\u00d7D2\u00d7\u2026\u00d7Dn<\/li>\n<\/ol>\n<h3>Table<\/h3>\n<p>A database is composed of multiple tables and each<em>\u00a0<\/em>table holds the data. Figure 7.1 shows a database that contains three tables.<\/p>\n<figure id=\"attachment_29\" aria-describedby=\"caption-attachment-29\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Banking-Systems-RDBMS-300x195.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-29\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/School-Database-Fig-1-300x221.jpg\" alt=\"Blue cylinder with three white rectangles each with a list of words.\" width=\"300\" height=\"221\" \/><\/a><figcaption id=\"caption-attachment-29\" class=\"wp-caption-text\">Figure 7.1. Database with three tables.<\/figcaption><\/figure>\n<h3>Column<\/h3>\n<p>A database stores pieces of information or facts in an organized way. Understanding how to use and get the most out of databases requires us to understand that method of organization.<\/p>\n<p>The principal storage units are called <em>columns<\/em>\u00a0or <em>fields<\/em>\u00a0or <em>attributes<\/em>. These house the basic components of data into which\u00a0your content can be broken down. When deciding which fields to create, you need to think generically about your information, for example, drawing out the common components of the information that you will store in the database and avoiding the specifics that distinguish one item from another.<\/p>\n<p>Look at the example of an ID card in Figure 7.2 to see the relationship between fields and their data.<\/p>\n<figure id=\"attachment_41\" aria-describedby=\"caption-attachment-41\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-41 size-full\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177.jpg\" alt=\"Record-300x177\" width=\"300\" height=\"177\" srcset=\"https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177.jpg 300w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177-65x38.jpg 65w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Record-300x177-225x132.jpg 225w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-41\" class=\"wp-caption-text\">Figure 7.2. Example of an ID card by A. Watt.<\/figcaption><\/figure>\n<h3>Domain<\/h3>\n<p>A <em>domain<\/em> is the original sets of atomic values used to model data. By <em>atomic value<\/em>, we mean that each value in the domain is indivisible as far as the relational model is concerned. For example:<\/p>\n<ul>\n<li>The domain of Marital Status has a set of possibilities:\u00a0Married, Single, Divorced.<\/li>\n<li>The domain of Shift has the set of all possible days: {Mon, Tue, Wed\u2026}.<\/li>\n<li>The domain of Salary is the set of all floating-point numbers greater than 0 and less than 200,000.<\/li>\n<li>The domain of First Name is the set of character strings that represents names of people.<\/li>\n<\/ul>\n<p>In summary, a domain is a set of acceptable values that a column is allowed to contain. This is based on various properties and the data type for the column. We will discuss data types in another chapter.<\/p>\n<h3>Records<\/h3>\n<p>Just as the content of any one document or item needs to be broken down into its constituent bits of data for storage in the fields, the link between them also needs to be available so that they can be reconstituted into their whole form. Records allow us to do this. <em>Records<\/em> contain fields that are related, such as a customer or an employee. As noted earlier, a tuple is another term used for record.<\/p>\n<p>Records and fields form the basis of all databases. A simple table \u00a0gives us the clearest picture of how records and fields work together in a\u00a0database storage project.<\/p>\n<figure id=\"attachment_136\" aria-describedby=\"caption-attachment-136\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/RDBMS-300x2091.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-136\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Table-Description-300x146.jpg\" width=\"300\" height=\"146\" alt=\"image\" \/><\/a><figcaption id=\"caption-attachment-136\" class=\"wp-caption-text\">Figure 7.3. Example of a simple table by A. Watt.<\/figcaption><\/figure>\n<p>The<span style=\"color: #333333;\"> simple table<\/span> example in Figure 7.3 shows us how fields can hold a range of different sorts of data. This one has:<\/p>\n<ul>\n<li>A Record ID field: this is an ordinal number; its data type is an integer.<\/li>\n<li>A PubDate field: this is displayed as day\/month\/year; its data type is date.<\/li>\n<li>An Author field: this is displayed as\u00a0Initial. Surname; its data type is text.<\/li>\n<li>A Title field text: free text can be entered here.<\/li>\n<\/ul>\n<p>You can command the database to sift through its data and organize it in a particular way. For example, you can request that a selection of records be limited by date: 1. all before a given date, 2. all after a given date or 3. all between two given dates. Similarly, you can choose to have records sorted by date. Because the field, or record, containing the data is set up as a Date field, the database reads the information in the Date field not just as numbers separated by slashes, but rather, as dates that\u00a0must be ordered according to a calendar system.<\/p>\n<h3>Degree<\/h3>\n<p>The <em>degree<\/em> is the number of attributes in a table. In our example in Figure 7.3, the degree is 4.<\/p>\n<h2>Properties of a Table<\/h2>\n<ul>\n<li>A table has a name that is distinct from all other tables in the database.<\/li>\n<li>There are no duplicate rows; each row is distinct.<\/li>\n<li>Entries in columns are atomic. The table<span style=\"color: #333333;\">\u00a0does\u00a0<\/span>not contain repeating groups or multivalued attributes.<\/li>\n<li>Entries from columns are from the same domain based on their data type including:\n<ul>\n<li>number (numeric, integer, float, smallint,\u2026)<\/li>\n<li>character (string)<\/li>\n<li>date<\/li>\n<li>logical (true or false)<\/li>\n<\/ul>\n<\/li>\n<li>Operations combining different data types are disallowed.<\/li>\n<li>Each attribute has a distinct name.<\/li>\n<li>The sequence of columns is insignificant.<\/li>\n<li>The sequence of rows is insignificant.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Key Terms<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p><strong>atomic value<\/strong>:\u00a0each value in the domain is indivisible as far as the relational model is concerned<strong>attribute<\/strong>:\u00a0principle storage unit in a database<\/p>\n<p><strong>column: <\/strong>see <em>attribute<\/em><\/p>\n<p><strong>degree<\/strong>: number of attributes in a table<\/p>\n<p><strong>domain<\/strong>:\u00a0the original sets of atomic values used to model data;\u00a0a set of acceptable values that a column is allowed to contain<\/p>\n<p><strong>field<\/strong>:\u00a0see\u00a0<em>attribute<\/em><\/p>\n<p><strong>file<\/strong>:see<em> relation<\/em><\/p>\n<p><strong>record<\/strong>:\u00a0contains fields that are related; <em>see tuple<\/em><\/p>\n<p><strong>relation<\/strong>: a\u00a0subset of the Cartesian product of a list of domains characterized by a name; the technical term for table or file<\/p>\n<p><strong>row<\/strong>: <em>see tuple<\/em><\/p>\n<p><strong>structured query language (SQL)<\/strong>: the standard database access language<\/p>\n<p><strong>table:<\/strong>see<em> relation<\/em><\/p>\n<p><strong>tuple<\/strong>:\u00a0a technical term for row or record<\/p>\n<h4>Terminology Key<\/h4>\n<p>Several of the terms used in this chapter are synonymous. In addition to the Key Terms above, please refer to Table 7.1 below. The terms in the Alternative 1 column are most commonly used.<\/p>\n<figure id=\"attachment_43\" aria-describedby=\"caption-attachment-43\" style=\"width: 288px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-43 size-full\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms.jpg\" alt=\"A database table with words.\" width=\"288\" height=\"110\" srcset=\"https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms.jpg 288w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms-65x24.jpg 65w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2013\/12\/Terms-225x85.jpg 225w\" sizes=\"auto, (max-width: 288px) 100vw, 288px\" \/><\/a><figcaption id=\"caption-attachment-43\" class=\"wp-caption-text\">Table 7.1. Terms and their synonyms by A. Watt.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Exercises<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p><em> Use Table 7.2 to answer questions 1-4.<\/em><\/p>\n<ol>\n<li>Using correct terminology, identify and describe all the components \u00a0in Table 7.2.<\/li>\n<li>What is the possible domain for field EmpJobCode?<\/li>\n<li>How many records are shown?<\/li>\n<li>How many attributes are shown?<\/li>\n<li>List the properties of a table.<\/li>\n<\/ol>\n<figure id=\"attachment_249\" aria-describedby=\"caption-attachment-249\" style=\"width: 600px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-249\" src=\"http:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554.jpg\" alt=\"Table with 5 columns and 5 rows.\" width=\"600\" height=\"112\" srcset=\"https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554.jpg 1206w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554-300x56.jpg 300w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554-1024x191.jpg 1024w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554-65x12.jpg 65w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554-225x42.jpg 225w, https:\/\/opentextbc.ca\/dbdesign01\/wp-content\/uploads\/sites\/11\/2014\/03\/Ch7-Exercises-Fig7-1-e1409190387554-350x65.jpg 350w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/a><figcaption id=\"caption-attachment-249\" class=\"wp-caption-text\">Table 7.2. Table for exercise questions, by A. Watt.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<h2>\u00a0Attribution<\/h2>\n<p><span style=\"color: #1f1f1d;\">This chapter of\u00a0<\/span><em style=\"color: #1f1f1d;\">Database Design<\/em><span style=\"color: #1f1f1d;\"> (including images, except as otherwise noted) is a derivative copy of\u00a0<a href=\"http:\/\/cnx.org\/contents\/e5ac0441-0e54-4895-9112-fb3a4ee9bce1@1\">Relational Design Theory<\/a><\/span><span style=\"color: #1f1f1d;\">\u00a0by<\/span>\u00a0Nguyen Kim Anh<span style=\"color: #1f1f1d;\">\u00a0licensed under\u00a0<\/span><a style=\"color: #870d0d;\" href=\"http:\/\/creativecommons.org\/licenses\/by\/3.0\/\">Creative Commons Attribution License 3.0 license<\/a><\/p>\n<p>The following material was written by Adrienne Watt:<\/p>\n<ol>\n<li>All or part of the sections on relations, tables, columns and degree<\/li>\n<li>Key Terms<\/li>\n<li>Exercises<\/li>\n<\/ol>\n","protected":false},"author":1,"menu_order":7,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["adrienne-watt"],"pb_section_license":""},"chapter-type":[],"contributor":[47],"license":[],"class_list":["post-44","chapter","type-chapter","status-publish","hentry","contributor-adrienne-watt"],"part":3,"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/44","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":26,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/44\/revisions"}],"predecessor-version":[{"id":1159,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/44\/revisions\/1159"}],"part":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapters\/44\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/media?parent=44"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/pressbooks\/v2\/chapter-type?post=44"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/contributor?post=44"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/dbdesign01\/wp-json\/wp\/v2\/license?post=44"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}