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Postgresql serial1/6/2023 ![]() Postgresql serial serial#Declaring a database table column as type SERIAL satisfies the requirement for synthetic keys by supplying unique integers upon inserts of new tuples. PostgreSQL provides a special datatype declaration to satisfy this need for synthetic keys. social security number, are neither: a person can obtain a new SSN, and SSN’s sometimes are re-used. Even some values commonly thought by laypersons to be unique and immutable, such as the U.S. In additional to the simplicity of a single column key, the fact that there is no real-world dependency means that external factors can never force a need to change the value, such as for instance, might be the case if a person’s name where used as a key … and then the person married or entered a federal government witness protection program and changed their name. That is, rather than relying on some combination of actual attributes, a value internal to the database, typically incremented integer values, and otherwise having no physical meaning is defined as a key. Some purists maintain that any modeled object or concept inherently possesses an attribute or set of attributes that can serve as a key and that it is important to identify this set of key attributes and utilize them for the unique selection of tuples.īut as a practical matter, identifying a sufficiently large set of attributes assurring uniqueness for a modeled object may be impractical, and so for real-world implementations, developers often turn to synthetic keys as a surrogate. The attributes, or columns, that together distinctly identify one tuple from all the others are called a “key”. ![]() ![]() Unique KeysĪ foundational precept of database design theory is that each tuple (i.e., row) of a relation (i.e., table) must be uniquely identified from other tuples. This article introduces the special implementation of serial data types typically used for creation of synthetic primary keys. PostgreSQL natively supplies a rich diversity of data types supporting many practical use cases. ![]()
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