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📄 Contents

  1. SQL Server Reference Guide
  2. Introduction
  3. SQL Server Reference Guide Overview
  4. Table of Contents
  5. Microsoft SQL Server Defined
  6. SQL Server Editions
  7. SQL Server Access
  8. Informit Articles and Sample Chapters
  9. Online Resources
  10. Microsoft SQL Server Features
  11. SQL Server Books Online
  12. Clustering Services
  13. Data Transformation Services (DTS) Overview
  14. Replication Services
  15. Database Mirroring
  16. Natural Language Processing (NLP)
  17. Analysis Services
  18. Microsot SQL Server Reporting Services
  19. XML Overview
  20. Notification Services for the DBA
  21. Full-Text Search
  22. SQL Server 2005 - Service Broker
  23. Using SQL Server as a Web Service
  24. SQL Server Encryption Options Overview
  25. SQL Server 2008 Overview
  26. SQL Server 2008 R2 Overview
  27. SQL Azure
  28. The Utility Control Point and Data Application Component, Part 1
  29. The Utility Control Point and Data Application Component, Part 2
  30. Microsoft SQL Server Administration
  31. The DBA Survival Guide: The 10 Minute SQL Server Overview
  32. Preparing (or Tuning) a Windows System for SQL Server, Part 1
  33. Preparing (or Tuning) a Windows System for SQL Server, Part 2
  34. Installing SQL Server
  35. Upgrading SQL Server
  36. SQL Server 2000 Management Tools
  37. SQL Server 2005 Management Tools
  38. SQL Server 2008 Management Tools
  39. SQL Azure Tools
  40. Automating Tasks with SQL Server Agent
  41. Run Operating System Commands in SQL Agent using PowerShell
  42. Automating Tasks Without SQL Server Agent
  43. Storage – SQL Server I/O
  44. Service Packs, Hotfixes and Cumulative Upgrades
  45. Tracking SQL Server Information with Error and Event Logs
  46. Change Management
  47. SQL Server Metadata, Part One
  48. SQL Server Meta-Data, Part Two
  49. Monitoring - SQL Server 2005 Dynamic Views and Functions
  50. Monitoring - Performance Monitor
  51. Unattended Performance Monitoring for SQL Server
  52. Monitoring - User-Defined Performance Counters
  53. Monitoring: SQL Server Activity Monitor
  54. SQL Server Instances
  55. DBCC Commands
  56. SQL Server and Mail
  57. Database Maintenance Checklist
  58. The Maintenance Wizard: SQL Server 2000 and Earlier
  59. The Maintenance Wizard: SQL Server 2005 (SP2) and Later
  60. The Web Assistant Wizard
  61. Creating Web Pages from SQL Server
  62. SQL Server Security
  63. Securing the SQL Server Platform, Part 1
  64. Securing the SQL Server Platform, Part 2
  65. SQL Server Security: Users and other Principals
  66. SQL Server Security – Roles
  67. SQL Server Security: Objects (Securables)
  68. Security: Using the Command Line
  69. SQL Server Security - Encrypting Connections
  70. SQL Server Security: Encrypting Data
  71. SQL Server Security Audit
  72. High Availability - SQL Server Clustering
  73. SQL Server Configuration, Part 1
  74. SQL Server Configuration, Part 2
  75. Database Configuration Options
  76. 32- vs 64-bit Computing for SQL Server
  77. SQL Server and Memory
  78. Performance Tuning: Introduction to Indexes
  79. Statistical Indexes
  80. Backup and Recovery
  81. Backup and Recovery Examples, Part One
  82. Backup and Recovery Examples, Part Two: Transferring Databases to Another System (Even Without Backups)
  83. SQL Profiler - Reverse Engineering An Application
  84. SQL Trace
  85. SQL Server Alerts
  86. Files and Filegroups
  87. Partitioning
  88. Full-Text Indexes
  89. Read-Only Data
  90. SQL Server Locks
  91. Monitoring Locking and Deadlocking
  92. Controlling Locks in SQL Server
  93. SQL Server Policy-Based Management, Part One
  94. SQL Server Policy-Based Management, Part Two
  95. SQL Server Policy-Based Management, Part Three
  96. Microsoft SQL Server Programming
  97. An Outline for Development
  98. Database
  99. Database Services
  100. Database Objects: Databases
  101. Database Objects: Tables
  102. Database Objects: Table Relationships
  103. Database Objects: Keys
  104. Database Objects: Constraints
  105. Database Objects: Data Types
  106. Database Objects: Views
  107. Database Objects: Stored Procedures
  108. Database Objects: Indexes
  109. Database Objects: User Defined Functions
  110. Database Objects: Triggers
  111. Database Design: Requirements, Entities, and Attributes
  112. Business Process Model Notation (BPMN) and the Data Professional
  113. Business Questions for Database Design, Part One
  114. Business Questions for Database Design, Part Two
  115. Database Design: Finalizing Requirements and Defining Relationships
  116. Database Design: Creating an Entity Relationship Diagram
  117. Database Design: The Logical ERD
  118. Database Design: Adjusting The Model
  119. Database Design: Normalizing the Model
  120. Creating The Physical Model
  121. Database Design: Changing Attributes to Columns
  122. Database Design: Creating The Physical Database
  123. Database Design Example: Curriculum Vitae
  124. NULLs
  125. The SQL Server Sample Databases
  126. The SQL Server Sample Databases: pubs
  127. The SQL Server Sample Databases: NorthWind
  128. The SQL Server Sample Databases: AdventureWorks
  129. The SQL Server Sample Databases: Adventureworks Derivatives
  130. UniversalDB: The Demo and Testing Database, Part 1
  131. UniversalDB: The Demo and Testing Database, Part 2
  132. UniversalDB: The Demo and Testing Database, Part 3
  133. UniversalDB: The Demo and Testing Database, Part 4
  134. Getting Started with Transact-SQL
  135. Transact-SQL: Data Definition Language (DDL) Basics
  136. Transact-SQL: Limiting Results
  137. Transact-SQL: More Operators
  138. Transact-SQL: Ordering and Aggregating Data
  139. Transact-SQL: Subqueries
  140. Transact-SQL: Joins
  141. Transact-SQL: Complex Joins - Building a View with Multiple JOINs
  142. Transact-SQL: Inserts, Updates, and Deletes
  143. An Introduction to the CLR in SQL Server 2005
  144. Design Elements Part 1: Programming Flow Overview, Code Format and Commenting your Code
  145. Design Elements Part 2: Controlling SQL's Scope
  146. Design Elements Part 3: Error Handling
  147. Design Elements Part 4: Variables
  148. Design Elements Part 5: Where Does The Code Live?
  149. Design Elements Part 6: Math Operators and Functions
  150. Design Elements Part 7: Statistical Functions
  151. Design Elements Part 8: Summarization Statistical Algorithms
  152. Design Elements Part 9:Representing Data with Statistical Algorithms
  153. Design Elements Part 10: Interpreting the Data—Regression
  154. Design Elements Part 11: String Manipulation
  155. Design Elements Part 12: Loops
  156. Design Elements Part 13: Recursion
  157. Design Elements Part 14: Arrays
  158. Design Elements Part 15: Event-Driven Programming Vs. Scheduled Processes
  159. Design Elements Part 16: Event-Driven Programming
  160. Design Elements Part 17: Program Flow
  161. Forming Queries Part 1: Design
  162. Forming Queries Part 2: Query Basics
  163. Forming Queries Part 3: Query Optimization
  164. Forming Queries Part 4: SET Options
  165. Forming Queries Part 5: Table Optimization Hints
  166. Using SQL Server Templates
  167. Transact-SQL Unit Testing
  168. Index Tuning Wizard
  169. Unicode and SQL Server
  170. SQL Server Development Tools
  171. The SQL Server Transact-SQL Debugger
  172. The Transact-SQL Debugger, Part 2
  173. Basic Troubleshooting for Transact-SQL Code
  174. An Introduction to Spatial Data in SQL Server 2008
  175. Performance Tuning
  176. Performance Tuning SQL Server: Tools and Processes
  177. Performance Tuning SQL Server: Tools Overview
  178. Creating a Performance Tuning Audit - Defining Components
  179. Creating a Performance Tuning Audit - Evaluation Part One
  180. Creating a Performance Tuning Audit - Evaluation Part Two
  181. Creating a Performance Tuning Audit - Interpretation
  182. Creating a Performance Tuning Audit - Developing an Action Plan
  183. Understanding SQL Server Query Plans
  184. Performance Tuning: Implementing Indexes
  185. Performance Monitoring Tools: Windows 2008 (and Higher) Server Utilities, Part 1
  186. Performance Monitoring Tools: Windows 2008 (and Higher) Server Utilities, Part 2
  187. Performance Monitoring Tools: Windows System Monitor
  188. Performance Monitoring Tools: Logging with System Monitor
  189. Performance Monitoring Tools: User Defined Counters
  190. General Transact-SQL (T-SQL) Performance Tuning, Part 1
  191. General Transact-SQL (T-SQL) Performance Tuning, Part 2
  192. General Transact-SQL (T-SQL) Performance Tuning, Part 3
  193. Performance Monitoring Tools: An Introduction to SQL Profiler
  194. Performance Tuning: Introduction to Indexes
  195. Performance Monitoring Tools: SQL Server 2000 Index Tuning Wizard
  196. Performance Monitoring Tools: SQL Server 2005 Database Tuning Advisor
  197. Performance Monitoring Tools: SQL Server Management Studio Reports
  198. Performance Monitoring Tools: SQL Server 2008 Activity Monitor
  199. The SQL Server 2008 Management Data Warehouse and Data Collector
  200. Performance Monitoring Tools: Evaluating Wait States with PowerShell and Excel
  201. Practical Applications
  202. Choosing the Back End
  203. The DBA's Toolbox, Part 1
  204. The DBA's Toolbox, Part 2
  205. Scripting Solutions for SQL Server
  206. Building a SQL Server Lab
  207. Using Graphics Files with SQL Server
  208. Enterprise Resource Planning
  209. Customer Relationship Management (CRM)
  210. Building a Reporting Data Server
  211. Building a Database Documenter, Part 1
  212. Building a Database Documenter, Part 2
  213. Data Management Objects
  214. Data Management Objects: The Server Object
  215. Data Management Objects: Server Object Methods
  216. Data Management Objects: Collections and the Database Object
  217. Data Management Objects: Database Information
  218. Data Management Objects: Database Control
  219. Data Management Objects: Database Maintenance
  220. Data Management Objects: Logging the Process
  221. Data Management Objects: Running SQL Statements
  222. Data Management Objects: Multiple Row Returns
  223. Data Management Objects: Other Database Objects
  224. Data Management Objects: Security
  225. Data Management Objects: Scripting
  226. Powershell and SQL Server - Overview
  227. PowerShell and SQL Server - Objects and Providers
  228. Powershell and SQL Server - A Script Framework
  229. Powershell and SQL Server - Logging the Process
  230. Powershell and SQL Server - Reading a Control File
  231. Powershell and SQL Server - SQL Server Access
  232. Powershell and SQL Server - Web Pages from a SQL Query
  233. Powershell and SQL Server - Scrubbing the Event Logs
  234. SQL Server 2008 PowerShell Provider
  235. SQL Server I/O: Importing and Exporting Data
  236. SQL Server I/O: XML in Database Terms
  237. SQL Server I/O: Creating XML Output
  238. SQL Server I/O: Reading XML Documents
  239. SQL Server I/O: Using XML Control Mechanisms
  240. SQL Server I/O: Creating Hierarchies
  241. SQL Server I/O: Using HTTP with SQL Server XML
  242. SQL Server I/O: Using HTTP with SQL Server XML Templates
  243. SQL Server I/O: Remote Queries
  244. SQL Server I/O: Working with Text Files
  245. Using Microsoft SQL Server on Handheld Devices
  246. Front-Ends 101: Microsoft Access
  247. Comparing Two SQL Server Databases
  248. English Query - Part 1
  249. English Query - Part 2
  250. English Query - Part 3
  251. English Query - Part 4
  252. English Query - Part 5
  253. RSS Feeds from SQL Server
  254. Using SQL Server Agent to Monitor Backups
  255. Reporting Services - Creating a Maintenance Report
  256. SQL Server Chargeback Strategies, Part 1
  257. SQL Server Chargeback Strategies, Part 2
  258. SQL Server Replication Example
  259. Creating a Master Agent and Alert Server
  260. The SQL Server Central Management System: Definition
  261. The SQL Server Central Management System: Base Tables
  262. The SQL Server Central Management System: Execution of Server Information (Part 1)
  263. The SQL Server Central Management System: Execution of Server Information (Part 2)
  264. The SQL Server Central Management System: Collecting Performance Metrics
  265. The SQL Server Central Management System: Centralizing Agent Jobs, Events and Scripts
  266. The SQL Server Central Management System: Reporting the Data and Project Summary
  267. Time Tracking for SQL Server Operations
  268. Migrating Departmental Data Stores to SQL Server
  269. Migrating Departmental Data Stores to SQL Server: Model the System
  270. Migrating Departmental Data Stores to SQL Server: Model the System, Continued
  271. Migrating Departmental Data Stores to SQL Server: Decide on the Destination
  272. Migrating Departmental Data Stores to SQL Server: Design the ETL
  273. Migrating Departmental Data Stores to SQL Server: Design the ETL, Continued
  274. Migrating Departmental Data Stores to SQL Server: Attach the Front End, Test, and Monitor
  275. Tracking SQL Server Timed Events, Part 1
  276. Tracking SQL Server Timed Events, Part 2
  277. Patterns and Practices for the Data Professional
  278. Managing Vendor Databases
  279. Consolidation Options
  280. Connecting to a SQL Azure Database from Microsoft Access
  281. SharePoint 2007 and SQL Server, Part One
  282. SharePoint 2007 and SQL Server, Part Two
  283. SharePoint 2007 and SQL Server, Part Three
  284. Querying Multiple Data Sources from a Single Location (Distributed Queries)
  285. Importing and Exporting Data for SQL Azure
  286. Working on Distributed Teams
  287. Professional Development
  288. Becoming a DBA
  289. Certification
  290. DBA Levels
  291. Becoming a Data Professional
  292. SQL Server Professional Development Plan, Part 1
  293. SQL Server Professional Development Plan, Part 2
  294. SQL Server Professional Development Plan, Part 3
  295. Evaluating Technical Options
  296. System Sizing
  297. Creating a Disaster Recovery Plan
  298. Anatomy of a Disaster (Response Plan)
  299. Database Troubleshooting
  300. Conducting an Effective Code Review
  301. Developing an Exit Strategy
  302. Data Retention Strategy
  303. Keeping Your DBA/Developer Job in Troubled Times
  304. The SQL Server Runbook
  305. Creating and Maintaining a SQL Server Configuration History, Part 1
  306. Creating and Maintaining a SQL Server Configuration History, Part 2
  307. Creating an Application Profile, Part 1
  308. Creating an Application Profile, Part 2
  309. How to Attend a Technical Conference
  310. Tips for Maximizing Your IT Budget This Year
  311. The Importance of Blue-Sky Planning
  312. Application Architecture Assessments
  313. Transact-SQL Code Reviews, Part One
  314. Transact-SQL Code Reviews, Part Two
  315. Cloud Computing (Distributed Computing) Paradigms
  316. NoSQL for the SQL Server Professional, Part One
  317. NoSQL for the SQL Server Professional, Part Two
  318. Object-Role Modeling (ORM) for the Database Professional
  319. Business Intelligence
  320. BI Explained
  321. Developing a Data Dictionary
  322. BI Security
  323. Gathering BI Requirements
  324. Source System Extracts and Transforms
  325. ETL Mechanisms
  326. Business Intelligence Landscapes
  327. Business Intelligence Layouts and the Build or Buy Decision
  328. A Single Version of the Truth
  329. The Operational Data Store (ODS)
  330. Data Marts – Combining and Transforming Data
  331. Designing Data Elements
  332. The Enterprise Data Warehouse — Aggregations and the Star Schema
  333. On-Line Analytical Processing (OLAP)
  334. Data Mining
  335. Key Performance Indicators
  336. BI Presentation - Client Tools
  337. BI Presentation - Portals
  338. Implementing ETL - Introduction to SQL Server 2005 Integration Services
  339. Building a Business Intelligence Solution, Part 1
  340. Building a Business Intelligence Solution, Part 2
  341. Building a Business Intelligence Solution, Part 3
  342. Tips and Troubleshooting
  343. SQL Server and Microsoft Excel Integration
  344. Tips for the SQL Server Tools: SQL Server 2000
  345. Tips for the SQL Server Tools – SQL Server 2005
  346. Transaction Log Troubles
  347. SQL Server Connection Problems
  348. Orphaned Database Users
  349. Additional Resources
  350. Tools and Downloads
  351. Utilities (Free)
  352. Tool Review (Free): DBDesignerFork
  353. Aqua Data Studio
  354. Microsoft SQL Server Best Practices Analyzer
  355. Utilities (Cost)
  356. Quest Software's TOAD for SQL Server
  357. Quest Software's Spotlight on SQL Server
  358. SQL Server on Microsoft's Virtual PC
  359. Red Gate SQL Bundle
  360. Microsoft's Visio for Database Folks
  361. Quest Capacity Manager
  362. SQL Server Help
  363. Visual Studio Team Edition for Database Professionals
  364. Microsoft Assessment and Planning Solution Accelerator
  365. Aggregating Server Data from the MAPS Tool

We're continuing our study of programming SQL Server databases with the next object after databases: tables. Tables are the absolute heart of Relational Database Management Systems, and a solid understanding here will help you immensely as we go along.

I'll go from the general to the specific in this article – but there's a lot to this topic. Don't worry; just keep this introduction handy, since we'll see table structure all throughout the development cycle. I've also included some really good links on this topic, plus several books in the Safari online service from InformIT. Ready? Here we go!

Tables Described

The concept of tables is really quite simple. Think of a series of rows and columns, like a spreadsheet. The columns represent the grouping of the data, and the rows represent the unique sets of data. The "cell," or the single intersection of a row and column, contains a single datum.

The relational database concept (which shares many concepts with set theory from algebra) has a few specific words for all this. Not that many people use them any more, but you might as well be familiar with them:

Table

Entity

Column

Attribute

Row

Tuple, or Record

Cell

Item, value, intersection


I'll use the more common names on the left throughout this tutorial.

So what might a table look like? Well, from the pubs sample database in SQL Server, here is a small set that I've selected:

au_id

au_lname

au_fname

phone

address

city

state

zip

contract

172-32-1176

White

Johnson

408 496-7223

10932 Bigge Rd.

Menlo Park

CA

94025

1

213-46-8915

Green

Marjorie

415 986-7020

309 63rd St. #411

Oakland

CA

94618

1

238-95-7766

Carson

Cheryl

415 548-7723

589 Darwin Ln.

Berkeley

CA

94705

1

267-41-2394

O'Leary

Michael

408 286-2428

22 Cleveland Av. #14

San Jose

CA

95128

1

274-80-9391

Straight

Dean

415 834-2919

5420 College Av.

Oakland

CA

94609

1


This sample is from the "authors" table. You can see that each row makes a record, and obviously contains information about individual authors. Here's another sample set:

title_id

title

type

pub_id

price

advance

royalty

ytd_sales

notes

pubdate

PS3333

Prolonged Data Deprivation: Four Case Studies

psychology

0736

19.99

2000

10

4072

What happens when the data runs dry? Searching evaluations of information-shortage effects.

6/12/1991

PS7777

Emotional Security: A New Algorithm

psychology

0736

7.99

4000

10

3336

Protecting yourself and your loved ones from undue emotional stress in the modern world. Use of computer and nutritional aids emphasized.

6/12/1991

TC3218

Onions, Leeks, and Garlic: Cooking Secrets of the Mediterranean

trad_cook

0877

20.95

7000

10

375

Profusely illustrated in color, this makes a wonderful gift book for a cuisine-oriented friend.

10/21/1991

TC4203

Fifty Years in Buckingham Palace Kitchens

trad_cook

0877

11.95

4000

14

15096

More anecdotes from the Queen's favorite cook describing life among English royalty. Recipes, techniques, tender vignettes.

6/12/1991

TC7777

Sushi, Anyone?

trad_cook

0877

14.99

8000

10

4095

Detailed instructions on how to make authentic Japanese sushi in your spare time.

6/12/1991


These are titles of books written, and this table has rows and columns representing information about books.

Now that we've covered the individual tables, we move to the reason that they make up the heart of the Relational Database Management System.

Relating Tables

Individual tables normally store the most absolute atomic level of data. By "atomic," I mean that only the data that belongs to the entity is stored in it. Information about the author should only be about the author – not his or her books. We'll come back to that in a bit, during the database design phase. (As a matter of fact, you'll come back to this over and over in your career, and you'll have some fairly heated arguments with your colleagues about what goes in a particular table!) This process is called table normalization, and it has several levels. For now, know that the entire basis of Relational Database Systems is based on this concept of keeping the table data atomic.

Back to the subject at hand. The individual tables are a nice, tight structure in which to store data, but they don't seem to have anything in common. As a matter of fact, from the data shown, you can't figure out which book was written by which author.

To solve this problem, we can add a column in one of the tables that points to the other, or relates them. That's done quite often in SQL, and is perfectly acceptable as long as once piece of data only relates to another one time (called a one to one relationship).

For instance, we could add a column in the second table that has the author's last name in it, showing who wrote that book. That may work, but two authors might have the same last name. Plus, storing the name (or almost any data) in two different tables can often lead to trouble, since you have to remember that if the information changes in one table, you have to change it in all the others.

Another problem arises in this situation if more than one author writes a single book. This is called a one-to-many relationship. I've worked on several projects like that – both as an author and as a SQL-guy! Would you add one column for the other author, two (in the two-author case), three, more?

You can solve this problem with a table that has a column for the author link, and another column for the title of the books. The link for the author would repeat in several records, but the book titles would be different.

You can see that the problem would also carry through the other way round. That is, if we tried to add a column for the books in the author's table, how many should we add? Again, this problem can be solved with a link to the book titles written, with the author appearing only once.

But often both situations occur at the same time. More than one author can write more than one book. This situation is called a many-to-many relationship. How do we resolve that dilemma? With one more table.

Here's what that table looks like in the pubs database:

au_id

Title_id

au_ord

royaltyper

172-32-1176

PS3333

1

100

213-46-8915

BU1032

2

40

213-46-8915

BU2075

1

100

238-95-7766

PC1035

1

100

267-41-2394

BU1111

2

40


You can probably guess how this helps. By combining the three tables, we pull the au_id from the first table, the title_id from the second and connect those using the third table. I've highlighted the values in question and placed the third table in the middle:

Authors

au_id

au_lname

au_fname

phone

address

city

state

zip

contract

172-32-1176

White

Johnson

408 496-7223

10932 Bigge Rd.

Menlo Park

CA

94025

1


TitleAuthors

au_id

Title_id

au_ord

royaltyper

172-32-1176

PS3333

1

100


Titles

title_id

Title

type

pub_id

price

advance

royalty

ytd_sales

notes

pubdate

PS3333

Prolonged Data Deprivation: Four Case Studies

psychology

0736

19.99

2000

10

4072

What happens when the data runs dry? Searching evaluations of information-shortage effects.

6/12/1991


The middle table shown above provides the "link" between the other two tables. Actually, the middle table can be used to join many tables. This joining of tables is analogous to the concept of the union in algebra set theory.

To be sure, there's more to know about these relationships, but I've hit you with enough new info for now. We'll revisit this topic in future articles on development, called Logical Database Design.

For now, let's look at how SQL Server physically implements tables, and then how to create them.

How SQL Server 2000 Implements Tables

SQL Server 2000 pretty much complies with the ANSI-92 SQL Standards. Those standards are the base-level requirements for creating, destroying and managing tables. The ANSI standard sets the minimums, and then each vendor then extends that minimum to sell their product.

Here are some quick facts about SQL Server 2000 tables:

  • Tables have owners

  • Tables can be stored on various SQL Filenames

  • You can store 8060 bytes per row of data in a table

  • You can have 1024 columns per table

  • You can have 2,147,483,647 objects in a database, and the number of tables is part of this maximum

  • You can store 1,048,516 TB of data in a SQL Server database, so the total storage of all tables must be kept under this number

Creating Tables

There are several ways to create tables, from using graphical tools, to typing Transact-SQL (T-SQL) commands to programming. I'll show you how to use the graphical tools and then the T-SQL method. We'll discuss programming in another article.

The first method I teach for creating tables is with a great tool, the Table Designer. You can see in the graphic below that I've opened Enterprise Manager and drilled down to the Test database object.

Figure 59Figure 59

I then right-clicked the Tables object and selected New Table from the menu that appeared. I continue the process on this panel:

Figure 60Figure60

You can see here that I'm setting the name of the columns in my table and giving them a data type (I'll cover data types in greater depth in another article) and length.

The part I wanted to point out here is the Allow Nulls selection. I'll explain Nulls more completely when we begin coding, but a Null condition means basically "I don't know yet." It doesn't mean zero, it doesn't mean nothing, it means "I don't know yet." As a matter of fact, there is still a bit of argument going around on whether you should even be allowed to have a Null value in a database.

While I won't take sides on this issue (some people need to get out more!) I will say that you should carefully consider whether you should allow a value to be Null. Here's a basic rule of thumb: If you're going to compare this value to something else, then you should think long and hard about allowing a Null value. Think of it like this:

I don't know how much money I have in my pocket. You walk up and say, "How much money do you have?" I say, "I don't know." You then ask, "Do you have more than Carl? He's got ten dollars." I reply "I don't know; I might." You ask, "Do you have exactly what Christine has? She has five dollars." I reply "I don't know. I might have that much, or none. I just don't know."

You see, you can never be sure what I have, so you can't trust any answer I give. For that reason, you shouldn't compare values to a Null value. In listing the number of people who have five dollars in their pocket, you really can't count me in or out of that set.

Even though I've said all this, I'll make quite a few of my columns to allow a Null that really shouldn't be, so we can see the problems that it creates later.

OK, I've beat that concept to death! Let's move on.

The next panel has all the columns filled out, and you can see that I've also created a value to hold the key for this table, which is the unique value assigned to each row. It's easy to do – just highlight the column and click the key icon. I've set the Identity attribute to be true on this Integer column, which means that SQL Server will generate a new number for me each time I enter a new record.

Figure 61Figure 61

I haven't covered all of the options here, since we'll use this tool again when we create our programming databases in future articles. I just wanted to expose the panels to you here.

Clicking the icon that looks like a scroll brings up the following panel:

Figure 62Figure 62

Here I'm setting the table name, owner, and so forth. The next tab on this panel is the Relationships tab, shown here:

Figure 63Figure 63

On this tab I can create relationships with other tables, just as we discussed earlier. This allows me to make sure that a "child" value from another table checks to make sure that a "parent" value exists in this one. I can also make this the "child" table, or have this table be a child to one table and a parent to another.

The next tab is shown here:

Figure 64Figure 64

I explained indexes in another set of articles, and here's how you can create them graphically. We'll see more of this tab later. The next tab sets the check constraints:

Figure 65Figure 65

A check constraint is another way you can make sure users and programs only put data in a field when it meets certain conditions. These constraints, along with others, are called Declarative Referential Integrity. That means that no matter how the code is prepared, you prevent anyone or thing from entering data you don't want in the database. If you forgo this type of constraint, it will be up to the developer to make sure the data is clean. That's called Programmatic Referential Integrity, and is less safe, for obvious reasons.

OK, that's the high level graphical method for creating a table. You can also create tables with T-SQL Commands. The syntax is quite extensive, and is described completely in Books Online, but here's the code to create the same table I just made:

CREATE TABLE UserNames (
 UserCode int IDENTITY (1, 1) NOT NULL,
 FirstName varchar (50) NULL,
 LastName varchar (50) NOT NULL,
 Address varchar (50) NULL,
 City varchar (50) NULL,
 State char (2) NOT NULL,
 PostalCode varchar (15) NULL 
) 
ON [PRIMARY]

The relevant parts here are the Null and Not Null qualifiers, which I'm sure you can decipher. Also note the IDENTITY qualifier, which creates that auto-incrementing (1 to start, then increment by 1 each time) value.

What you don't see here is the Primary Key constraint I set with the key icon earlier. I'll demonstrate adding that constraint in the next article.

There's an optional qualifier here: the ON [PRIMARY] keywords. This important command sets where the table lives. If you just have one file for all objects (as 90% of most databases do) then you don't need it. If you do make other files for the database (which I've described elsewhere on this site), remember that they aren't used unless you put this statement on your indexes or table creation statements. You want to place tables that are used most often on these other files to speed access to them.

Whew!

Well, once again, we've scratched the surface of one of the database objects. We've got several more to cover, and as mentioned, we'll be revisiting the table object quite often in our programming. See you soon!

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Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


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Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

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Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

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Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


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Marketing


Pearson may send or direct marketing communications to users, provided that

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Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


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Sale of Personal Information


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While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

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Links


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Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020