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Hi/Lo is an algorithm and a key generation strategy used for generating unique keys for use in a database as a primary key.It uses a sequence-based hi-lo pattern to generate values.
Key Name Definition Simple A key made from only one attribute. Concatenated A key made from more than one attribute joined together as a single key, such as part or whole name with a system generated number appended as often used for E-mail addresses. Compound: A key made from at least two attributes or simple keys, only simple keys exist in a ...
A candidate key, or simply a key, of a relational database is any set of columns that have a unique combination of values in each row, with the additional constraint that removing any column could produce duplicate combinations of values. A candidate key is a minimal superkey, [1] i.e., a superkey that does not contain a smaller one. Therefore ...
A surrogate key is frequently a sequential number (e.g. a Sybase or SQL Server "identity column", a PostgreSQL or Informix serial, an Oracle or SQL Server SEQUENCE or a column defined with AUTO_INCREMENT in MySQL). Some databases provide UUID/GUID as a possible data type for surrogate keys (e.g. PostgreSQL UUID [3] or SQL Server ...
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 ...
In contrast, a character entity reference refers to a character by the name of an entity which has the desired character as its replacement text. The entity must either be predefined (built into the markup language) or explicitly declared in a Document Type Definition (DTD). The format is the same as for any entity reference: &name;
Next to this name, a character can have one or more formal (normative) alias names. Such an alias name also follows the rules of a name: characters used (A-Z, -, 0-9, <space>) and not used (a-z, %, $, etc.). Alias names are also unique in the full name set (that is, all names and alias names are all unique in their combined set).
This list includes SQL reserved words – aka SQL reserved keywords, [1] [2] as the SQL:2023 specifies and some RDBMSs have added. Reserved words in SQL and related products In SQL:2023 [ 3 ]