Home > Articles > Data > MySQL

Data Types in MySQL

This chapter is from the book

This chapter is from the book

3.3 How MySQL Handles Invalid Data Values

Historically, the dominant principle for data handling in MySQL has been, “Garbage in, garbage out.” In other words, MySQL attempts to store any data value you give it, but if you don’t verify the value first before storing it, you may not like what you get back out. However, as of MySQL 5.0.2, several SQL modes are available that enable you to reject bad values and cause an error to occur instead. The following discussion first discusses how MySQL handles improper data by default, and then covers the changes that occur when you enable the various SQL modes that affect data handling.

By default, MySQL handles out-of-range or otherwise improper values as follows:

  • For numeric or TIME columns, values that are outside the legal range are clipped to the nearest endpoint of the range and the resulting value is stored.
  • For string columns other than ENUM or SET, strings that are too long are truncated to fit the maximum length of the column.
  • Assignments to an ENUM or SET column depend on the values that are listed as legal in the column definition. If you assign to an ENUM column a value that is not listed as an enumeration member, the error member is assigned instead (that is, the empty string that corresponds to the zero-valued member). If you assign to a SET column a value containing substrings that are not listed as set members, those strings drop out and the column is assigned a value consisting of the remaining members.
  • For date or time columns, illegal values are converted to the appropriate “zero” value for the type (see Table 3.15).

These conversions are reported as warnings for statements such as INSERT, REPLACE, UPDATE, LOAD DATA, and ALTER TABLE. You can use SHOW WARNINGS after executing one of those statements to see the warning messages.

To turn on stricter checking of inserted or updated data values, enable one of the following SQL modes:

mysql> SET sql_mode = 'STRICT_ALL_TABLES';
mysql> SET sql_mode = 'STRICT_TRANS_TABLES';

For transactional tables, both modes are identical: If an invalid or missing value is found, an error occurs, the statement aborts and rolls back, and has no effect. For non-transactional tables, the modes have the following effects:

  • For both modes, if an invalid or missing value is found in the first row of a statement that inserts or updates rows, an error occurs. The statement aborts and has no effect, which is similar to what happens for transactional tables.
  • If an error occurs after the first row in a statement that inserts or updates multiple rows, some rows already will have been modified. The two strict modes control whether the statement aborts at that point or continues to execute:
    • With STRICT_ALL_TABLES, an error occurs and the statement aborts. Rows affected earlier by the statement will already have been modified, so the result is a partial update.
    • With STRICT_TRANS_TABLES, MySQL aborts the statement for non-transactional tables only if doing so would have the same effect as for a transactional table. That is true only if the error occurs in the first row; an error in a later row leaves the earlier rows already changed. Those changes cannot be undone for a non-transactional table, so MySQL continues to execute the statement to avoid a partial update. It converts each invalid value to the closest legal value, as defined earlier in this section. For a missing value, MySQL sets the column to the implicit default for its data type. Implicit defaults were described in Section 3.2.3, “Specifying Column Default Values.”

Strict mode actually does not enable the strictest checking that MySQL can perform. You can enable any or all of the following modes to impose additional constraints on input data:

  • ERROR_FOR_DIVISION_BY_ZERO prevents entry of values if division by zero occurs in strict mode. (Without strict mode, a warning occurs and NULL is inserted.)
  • NO_ZERO_DATE prevents entry of the “zero” date value in strict mode.
  • NO_ZERO_IN_DATE prevents entry of incomplete date values that have a month or day part of zero in strict mode.

For example, to enable strict mode for all storage engines and also check for divide-by-zero errors, set the SQL mode like this:

mysql> SET sql_mode = 'STRICT_ALL_TABLES,ERROR_FOR_DIVISION_BY_ZERO';

To turn on strict mode and all of the additional restrictions, you can simply enable TRADITIONAL mode:

mysql> SET sql_mode = 'TRADITIONAL';

TRADITIONAL is shorthand for “both strict modes, plus a bunch of other restrictions.” This is more like the way that other “traditional” SQL DBMSs act with regard to data checking.

It is also possible to selectively weaken strict mode in some respects. If you enable the ALLOW_INVALID_DATES SQL mode, MySQL doesn’t perform full checking of date parts. Instead, it requires only that months be in the range from 1 to 12 and days be in the range from 1 to 31 (which allows invalid values such as '2000-02-30' or '2000-06-31'). Another way to suppress errors is to use the IGNORE keyword with INSERT or UPDATE statements. With IGNORE, statements that would result in an error due to invalid values result only in a warning.

The various options available give you the flexibility to choose the level of validity checking that is appropriate for your applications.

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