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  2. Primary key - Wikipedia

    en.wikipedia.org/wiki/Primary_key

    In the relational model of databases, a primary key is a designated attribute that can reliably identify and distinguish between each individual record in a table.The database creator can choose an existing unique attribute or combination of attributes from the table (a natural key) to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose ...

  3. Log trigger - Wikipedia

    en.wikipedia.org/wiki/Log_trigger

    Use of an immutable natural key as a primary key. In a good database design, a natural key which can change should not be considered as a "real" primary key. Use of a mutable natural key as a primary key (it is widely discouraged) where changes are propagated in every place where it is a foreign key. In such a case, the history table should be ...

  4. Identity column - Wikipedia

    en.wikipedia.org/wiki/Identity_column

    An identity column differs from a primary key in that its values are managed by the server and usually cannot be modified. In many cases an identity column is used as a primary key; however, this is not always the case. It is a common misconception that an identity column will enforce uniqueness; however, this is not the case. If you want to ...

  5. Unique key - Wikipedia

    en.wikipedia.org/wiki/Unique_key

    One of those keys per table may be designated the primary key; other keys are called alternate keys. Any key may consist of one or more attributes. For example, a Social Security Number might be a single attribute key for an employee; a combination of flight number and date might be a key consisting of two attributes for a scheduled flight.

  6. Persistent object identifier - Wikipedia

    en.wikipedia.org/wiki/Persistent_Object_Identifier

    In database design, a persistent object identifier (POID) is a unique identifier of a record on a table, used as the primary key.Important characteristics of a POID are that it does not carry business information and are not generally exported or otherwise made visible to data users; as such a POID has many of the characteristics of a surrogate key.

  7. Candidate key - Wikipedia

    en.wikipedia.org/wiki/Candidate_key

    Therefore, a relation can have multiple candidate keys, each with a different number of attributes. [2] Specific candidate keys are sometimes called primary keys, secondary keys or alternate keys. The columns in a candidate key are called prime attributes, [3] and a column that does not occur in any candidate key is called a non-prime attribute.

  8. Your Cholesterol Could Be A Key Indicator Of Dementia. A ...

    www.aol.com/lifestyle/cholesterol-could-key...

    Typically, dementia is associated with classic symptoms like confusion and memory loss. But new research finds that there could be a less obvious risk factor out there: your cholesterol levels ...

  9. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075.This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.