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  2. Referential integrity - Wikipedia

    en.wikipedia.org/wiki/Referential_integrity

    Referential integrity is a property of data stating that all its references are valid. In the context of relational databases, it requires that if a value of one attribute (column) of a relation (table) references a value of another attribute (either in the same or a different relation), then the referenced value must exist. [1]

  3. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    A derived table is the use of referencing an SQL subquery in a FROM clause. Essentially, the derived table is a subquery that can be selected from or joined to. The derived table functionality allows the user to reference the subquery as a table. The derived table is sometimes referred to as an inline view or a subselect.

  4. DomainKeys Identified Mail - Wikipedia

    en.wikipedia.org/wiki/DomainKeys_Identified_Mail

    DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in email (email spoofing), a technique often used in phishing and email spam. DKIM allows the receiver to check that an email that claimed to have come from a specific domain was indeed authorized by the owner of that domain. [ 1 ]

  5. Prepared statement - Wikipedia

    en.wikipedia.org/wiki/Prepared_statement

    Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.

  6. Unique key - Wikipedia

    en.wikipedia.org/wiki/Unique_key

    When the data model is instantiated into a physical database, it is the key that the system uses the most when accessing the table, or joining the tables together when selecting data. Alternate A non-primary key that can be used to identify only one row in a table. Alternate keys may be used like a primary key in a single-table select. Foreign

  7. Why did I receive an email from MAILER-DAEMON? - AOL Help

    help.aol.com/articles/what-is-a-mailer-daemon...

    The most common reason for a failed delivery is that the email address entered isn't valid. If the delivery failure message says the account doesn't exist double check the spelling of the address you entered. A single misplaced letter could cause a delivery failure.

  8. Email authentication - Wikipedia

    en.wikipedia.org/wiki/Email_authentication

    Email authentication, or validation, is a collection of techniques aimed at providing verifiable information about the origin of email messages by validating the domain ownership of any message transfer agents (MTA) who participated in transferring and possibly modifying a message.

  9. X.500 - Wikipedia

    en.wikipedia.org/wiki/X.500

    An end user who relies on the authenticity of a certificate being presented to a browser or email has no simple way to compare a forged certificate presented (perhaps which triggers a browser warning) with a valid certificate, without also being given the opportunity to validate the DN or Distinguished Name which was designed to be looked up in ...