Home > Articles

  • Print
  • + Share This
This chapter is from the book

Sorting with the ORDER BY Clause

So far in this chapter, we have expanded the SELECT statement (including the FROM clause) with the WHERE clause for filtering. Now we will expand the SELECT statement further with the ORDER BY clause. The ORDER BY clause is used to sort rows returned by a query.

CAUTION

The ORDER BY clause is always executed on filtered query results, namely after the WHERE clause. Obviously, if there is no WHERE clause, this does not apply.

ORDER BY Clause Syntax

The syntax for the SELECT statement, including details of the optional ORDER BY clause, is shown in Figure 3.5.

Figure 3.5Figure 3.5 ORDER BY clause syntax.

Following is a synopsis of the syntax diagram as shown in Figure 3.5:

  • The ORDER BY clause is optional and is used for sorting filtered row sets. Thus, a WHERE clause will always appear before an ORDER BY clause.

  • Elements in the ORDER BY clause can refer to columns, aliased columns, expressions (those expressions can be in the SELECT list or not), or positions of elements in the SELECT list.

  • Each element in an ORDER BY clause is sorted in ascending order by default. Each element can be forcibly sorted individually in ascending order (ASC) or descending order (DESC).

  • By default, in ascending order, NULL values will always be sorted last and thus appear last. In descending order NULL values will appear first. Sorted order of NULL values can be overridden using the NULLS FIRST clause and the NULLS LAST clause (the default). NULLS FIRST returns NULL values at the start of a query, and NULLS LAST returns NULL values at the end of a query.

Sorting Using the ORDER BY Clause

Rows in a query are sorted according to the sequence of elements listed in the ORDER BY clause, from left to right. Therefore, the leftmost ORDER BY clause element is the most significant sort parameter, and the rightmost element is the least important sort parameter.

Figure 3.6 shows a query of the ACTOR table sorting by TYPECAST within GENDER.

Figure 3.6Figure 3.6 The sequence of ORDER BY clause sorting.

In Figure 3.6 we can see that all females (F) are sorted before all males (M). The TYPECAST column is sorted within GENDER. As a result, Teri Garr as a Comedian appears before George Clooney as an Action Drama actor.

Sorting Methods

The following example sorts on a single column:

SELECT TITLE, RANK, REVIEW_RANK, YEAR FROM MOVIE ORDER BY TITLE;

The next example sorts on multiple columns, not in the order in which the columns are selected:

SELECT TITLE, RANK, REVIEW_RANK, YEAR FROM MOVIE
  ORDER BY YEAR,TITLE, RANK;

This example sorts columns both in the selected columns list and not in that list but in the accessed MOVIE table:

SELECT TITLE, RANK, REVIEW_RANK, YEAR FROM MOVIE
ORDER BY REVIEWS, LIST_PRICE, YEAR, TITLE, RANK;

The next query will produce exactly the same result as the preceding query using positions of select list elements. YEAR is in fourth position, TITLE is in first position, and RANK is in second position:

SELECT TITLE, RANK, REVIEW_RANK, YEAR FROM MOVIE
ORDER BY REVIEWS, LIST_PRICE, 4, 1, 2;

If you change the sequence of select list elements, you have to change position numbers as well. This query produces the same rows as before but with the columns in a different order:

SELECT YEAR, TITLE, RANK, REVIEW_RANK FROM MOVIE
ORDER BY REVIEWS, LIST_PRICE, 1, 2, 3;

You can sort using aliased columns, even including those not in the select list:

SELECT M.TITLE, M.LIST_PRICE * M.RANK AS PROJSALES FROM MOVIE M
ORDER BY M.YEAR, M.TITLE;

And following from the previous query, we can sort using expressions in the select list:

SELECT M.TITLE, M.LIST_PRICE * M.RANK AS PROJSALES FROM MOVIE M
ORDER BY PROJSALES;

You can even sort using an expression not in the query select list:

SELECT M.TITLE, M.LIST_PRICE * M.RANK AS PROJSALES FROM MOVIE M
ORDER BY M.YEAR / 1000;

NOTE

Sorting using expressions implies that PL/SQL user-defined procedures can be used to sort with as well. PL/SQL is out of the scope of this book.

It follows that we can combine different sorting methods in the same ORDER BY clause. The following example is sorted by a column select list position, a column name in the select list, a column name in the tables but not in the select list, and finally an expression:

SELECT TITLE, RANK, REVIEW_RANK, YEAR, LIST_PRICE * RANK AS PROJSALES
FROM MOVIE
ORDER BY 4, TITLE, RELEASE, PROJSALES;

Sorting Modifiers

We can modify the way in which each column within an ORDER BY clause is sorted as shown in Figure 3.5, the ORDER BY clause syntax diagram, by using the ASC | DESC and NULLS { FIRST | LAST } optional modifiers.

If you look closely at Figure 3.6 again, you will see that the last two females, Madelaine Kahn and Diane Lane, have no TYPECAST setting. Their TYPECAST column values are NULL because they have not been set to anything, not even a space character. The default setting is NULLS LAST, meaning that NULL values are sorted last, as in Figure 3.6. If we wanted to specify NULLS LAST explicitly, we could use the following query modification:

SELECT GENDER, TYPECAST, NAME FROM ACTOR
ORDER BY GENDER, TYPECAST NULLS LAST;

You could return the NULL TYPECAST rows at the beginning of the females by using the following modification:

SELECT GENDER, TYPECAST, NAME FROM ACTOR
ORDER BY GENDER, TYPECAST NULLS FIRST;

Now we can reorder the same query. Specify both of the individual columns as being ordered in descending order, placing males before females. Also, specify all TYPECAST values in reverse alphabetical order and NULLS FIRST:

SELECT GENDER, TYPECAST, NAME FROM ACTOR
ORDER BY GENDER DESC , TYPECAST DESC NULLS FIRST;

NOTE

A NULL value is logically undefined and thus cannot be sorted, and can be placed only at the start of a sort (NULLS FIRST) or at the end of a sort (NULLS LAST).

This chapter has expanded the SELECT statement with the WHERE clause and the ORDER BY clause to cater for filtering and sorting of returned rows, respectively. The next chapter is the first of two chapters examining some Oracle SQL reference material, essential at this stage, covering operators, conditions, pseudocolumns, and expressions.

  • + Share This
  • 🔖 Save To Your Account

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