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The SQL language is subdivided into several language elements, including: Keywords are words that are defined in the SQL language. They are either reserved (e.g. SELECT, COUNT and YEAR), or non-reserved (e.g. ASC, DOMAIN and KEY). List of SQL reserved words. Identifiers are names on database objects, like tables, columns and schemas. An ...
Unique keys are an alternative to the primary key of the relation. In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not ...
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 ...
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;
In Unicode, characters can have a unique name. A character can also have one or more alias names. An alias name can be an abbreviation, a C0 or C1 control name, a correction, an alternate name or a figment. An alias too is unique over all names and aliases, and therefore identifying.
The alt keys (there are two of them) are easy to find on any Windows device—there’s one on either side of the space bar. It’s easy to make any accent or symbol on a Windows keyboard once you ...
(non-Unicode name) ('Scarab' is an informal name for the generic currency sign) § Section sign: section symbol, section mark, double-s, 'silcrow' Pilcrow; Semicolon: Colon ℠ Service mark symbol: Trademark symbol / Slash (non-Unicode name) Division sign, Forward Slash: also known as "stroke" / Solidus (the most common of the slash symbols ...
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