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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 ...
This is a list of commands from the GNU Core Utilities for Unix environments. These commands can be found on Unix operating systems and most Unix-like operating systems. GNU Core Utilities include basic file, shell and text manipulation utilities. Coreutils includes all of the basic command-line tools that are expected in a POSIX system.
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
An example of a database that has not enforced referential integrity. In this example, there is a foreign key (artist_id) value in the album table that references a non-existent artist — in other words there is a foreign key value with no corresponding primary key value in the referenced table.
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. Every relation without NULL values will have at least one candidate key: Since there cannot be duplicate rows, the set of all columns is a superkey, and if that is not minimal, some subset of ...
The following example of a SELECT query returns a list of expensive books. The query retrieves all rows from the Book table in which the price column contains a value greater than 100.00. The result is sorted in ascending order by title. The asterisk (*) in the select list indicates that all columns of the Book table should be included in the ...
New features include a "fast migration" option to migrate the data from the command-line instead of the GUI, a SSL certificate generator, improved SQL auto-completion, a new table data import and export wizard, and MySQL Enterprise Firewall support. Version 6.3.8, MySQL Workbench for MacOS has incompatibilities with MacOS Sierra. [26]
Using a SELECT statement after the INSERT statement with a database-specific function that returns the generated primary key for the most recently inserted row. For example, LAST_INSERT_ID() for MySQL. Using a unique combination of elements from the original SQL INSERT in a subsequent SELECT statement.