Home > Articles > Certification > Microsoft Certification

This chapter is from the book

Removing Unwanted Data

Over time, data becomes obsolete and needs to be removed. You remove data by using the DELETE statement. It is extremely important to provide a condition when performing data deletions because it is easy to remove all data if you do not exercise caution. The following command removes all records from the specified table:

DELETE FROM Customers

If you would like to delete all rows, you can use the fast, nonlogged method TRUNCATE TABLE. This immediately frees all space used by indexes and data by that table. On the other hand, DELETE should be used when partial data removal is desired. Although both TRUNCATE TABLE and a DELETE statement with no WHERE clause remove all rows in a table, TRUNCATE TABLE is faster and uses fewer system and log resources. The DELETE statement removes rows one at a time, recording an entry in the transaction log for each row.

TRUNCATE TABLE removes data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the log. TRUNCATE TABLE removes all rows from a table, but the table structure and its columns, constraints, and indexes remain intact. The counter used by any identity columns is reset to the seed value for the column. If you want to retain the identity counter, you should use DELETE instead.

Directly Removing Records from a Table

The DELETE statement removes one or more records from a table, based on a condition in the WHERE clause. The following is a simplified sample DELETE statement:

DELETE FROM Products
   WHERE Discontinued = 1

In a fashion similar to that used to remove a single record via a positioned update, you could also create a procedure that performs a positioned deletion by using the DELETE statement with the WHERE CURRENT OF clause as part of a CURSOR operation.

Indirectly Removing Data from a Table

Removing data from a table can affect other tables if cascading deletions have been specified for a relationship. This could mean the removal of other records based on a single DELETE operation. Also, a relationship definition may prevent the deletion of data and return an error condition to the operation. Triggers, restore operations, and stored procedures are other processes that could indirectly delete records.

Escalating Privileges to Allow Deletion

You often need to have an application remove data from a database on the user's behalf. In cases where users with limited permissions need to delete data in a special circumstance, it is best to do so through a controlled and logged procedure.

You could create a stored procedure to perform the deletion and optionally log information about who is performing the task, when, and why the deletion occurred. If the user does not have the rights to delete records, the procedure could be executed under a user ID or role that has that permission.

Normally, during a session, permission checks are performed based on the user currently logged in. When an EXECUTE AS statement is run, the context of the session changes. This change lasts for the duration of the immediate scope. After the switch, permissions are checked against the login used in the EXECUTE AS operation. In essence, the user or login account is impersonated for the duration of the batch or module execution. This allows operations to be performed that the user context would not normally allow.

IMPERSONATE permissions must be granted to the individual running the process with the EXECUTE AS operation. If the user logged into the system is the database owner or a member of the sysadmin role, these permissions are inherited. In this respect, the owner or administrator can test processes with a reduced level of permission to ensure that security measures that are in place are functioning as expected.

Controlling Privileges by Using GRANT, DENY, and REVOKE

Permissions on objects in a database can be assigned to users and roles either directly, using the graphical tools, or programmatically, through the use of scripting. Groups and logins can be associated with users and roles and thus have permissions affect them within the database. Permissions can also be assigned directly to logins within the server that affect the systemwide functions that can be performed.

The T-SQL GRANT, DENY, REVOKE statements can be executed within a procedure to deal with permissions through process execution. DENY is the strongest of the three permissions; when assigned, it takes precedence over all other permissions. Therefore, you need to be careful never to deny permission to a resource for the public role because doing so effectively blocks everyone from using the resource.

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