Home > Articles

This chapter is from the book

You use the Relationships window to establish relationships between Access tables, as shown in Figure 3.5. To open the Relationships window, click Relationships on the toolbar with the Database window active or choose Relationships from the Tools menu. If you have not established any relationships, the Show Table dialog appears. The Show Table dialog allows you to add tables to the Relationships window.

Looking at the Relationships window, you can see the type of relationships that exists for each table. All the one-to-many and one-to-one relationships defined in a database are represented with a join line. If you enforce referential integrity between the tables involved in a one-to-many relationship, the join line between the tables appears with the number 1 on the one side of the relationship and with an infinity symbol (x) on the many side of the relationship. One-to-one relationships appear with a 1 on both ends of the join lines.

Figure 3.5Figure 3.5 The Relationships window enables you to view, add, modify, and remove relationships between tables.

Establishing a Relationship Between Two Tables

To establish a relationship between two tables, follow these six steps:

  1. Open the Relationships window.

  2. If it is the first time that you're opening the Relationships window of a particular database, the Show Table dialog appears. Select each table you want to relate and click Add.

  3. If you have already established relationships in the current database, the Relationships window appears. If the tables you want to include in the relationship do not appear, click the Show Table button on the toolbar or choose Show Table from the Relationships menu. To add the desired tables to the Relationships window, select a table, and then click Add. Repeat this process for each table you want to add. To select multiple tables at once, press Shift while clicking to select contiguous tables or press Ctrl while clicking to select noncontiguous tables; then click Add. Click Close when you are finished.

  4. Click and drag the field from one table to the matching field in the other table. The Edit Relationships dialog appears, as shown in Figure 3.6.

  5. Determine whether you want to establish referential integrity, and whether you want to cascade update related fields or cascade delete related records by enabling the appropriate check boxes. The section later in this chapter entitled "Establishing Referential Integrity" covers these topics.

  6. Click Create.

Figure 3.6Figure 3.6 The Edit Relationships dialog enables you to view and modify the relationships between the tables in a database.

Looking at Guidelines for Establishing Relationships

You must remember a few important things when establishing relationships. If you are not aware of these important gotchas, you could find yourself in some pretty hairy situations.

  • It is important to understand the correlation between the Relationships window and the actual relationships you have established within the database. The Relationships window lets you view and modify the existing relationships. When you establish relationships, Access creates the relationships the moment you click Create. You can delete the tables from the Relationships window (by selecting them and pressing Delete), but the relationships still will exist. (The "Modifying an Existing Relationship" section, which appears later in this chapter, covers the process of permanently removing relationships.) The Relationships window provides a visual blueprint of the relationships that you have established. If you modify the layout of the window by moving tables around, or by adding/removing tables to the window, Access prompts you to save the layout after you close the Relationships window. Access is not asking whether you want to save the relationships you have established; it is simply asking whether you want to save the visual layout of the window.

  • When adding tables to the Relationships window using the Show Tables dialog, it is easy to accidentally add the same table to the window many times. This is because the tables you are adding can hide behind the Show Tables dialog, or they can appear below the portion of the Relationships window that you are viewing. If this occurs, you'll see multiple occurrences of the same table when you close the Show Tables dialog. Access gives each occurrence of the table a different alias. You must remove the extra occurrences.

  • You also can add queries to the Relationships window by using the Show Tables dialog. Although rarely used, this might be useful if you regularly include the same queries within other queries and want to permanently establish a relationship between them.

  • If you remove tables from the Relationships window (this does not delete the relationships) and you want to once again show all relationships that exist in the database, click Show All Relationships on the toolbar or choose Show All from the Relationships menu. These processes show all existing relationships.

  • To delete a relationship, click the join line and press Delete.

Create a new database and add a table called tblCustomers, another called tblOrders, and a third called tblOrderDetails. The tables should have the following fields:

tblCustomers: CustomerID, CompanyName, Address, City, State, ZipCode

tblOrders: OrderID, CustomerID, OrderDate, ShipVIA

tblOrderDetails: OrderID, LineNumber, ItemID, Quantity, Price

  1. In the tblCustomers table, make the CustomerID field a Text field. Designate the CustomerID field as the primary key. Set the size of the field to 5. Make all other fields Text fields with their default properties.

  2. In the tblOrders table, set OrderID to the AutoNumber field type. Make the OrderID the primary key field. Make the CustomerID field a Text field with a field size of 5. Set the field type of the OrderDate field to Date, and the field type of the ShipVIA field to Number with a size of Long Integer.

  3. In the tblOrderDetails table, set the field type of the OrderID field to Number and make sure that the size is Long Integer. Set the field type of the LineNumber field to Number with a size of Long Integer. You should base the primary key of the table on the combination of the OrderID and LineNumber fields. The ItemID and Quantity fields should be the Number type with a size of Long Integer. The Price field should be the Currency type.

  4. To open the Relationships window, click Relationships on the toolbar with the Database window active. With the tblCustomers table in the Show Table dialog selected, hold down your Shift key and click to select the tblOrders table. Click Add. All three tables should appear in the Relationships window. Click Close. Click and drag from the CustomerID field in the tblCustomers table to the CustomerID field in the tblOrders table. After the Relationships dialog appears, click Create. Repeat the process, clicking and dragging the OrderID field from the tblOrders table to the OrderID field in the tblOrderDetails table.

NOTE

You can find this example, and all examples included in this chapter, in the Chap3TryIt.MDB file included with the sample code on the accompanying CD-ROM.

Modifying an Existing Relationship

Modifying an existing relationship is easy. Access gives you the capability to delete an existing relationship or to simply modify the nature of the relationship. To permanently remove a relationship between two tables, follow these three steps:

  1. With the Database window active, click Relationships on the toolbar.

  2. Click the line joining the two tables whose relationship you want to delete.

  3. Press Delete. Access prompts you to verify your actions. Click Yes.

You often will want to modify the nature of a relationship rather than remove it. To modify a relationship, follow these four steps:

  1. With the Database window active, click Relationships on the toolbar.

  2. Double-click the line joining the two tables whose relationship you want to modify.

  3. Make the required changes.

  4. Click OK. All the normal rules regarding the establishment of relationships will apply.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


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


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

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.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

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

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


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

Children


This site is not directed to children under the age of 13.

Marketing


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

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

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


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

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:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

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