Dominoes 49 glyphs, the same combinations vertically for another 49, and also a horizontal and a vertical "back" for a total of 100 glyphs. In this arrangement, both orientations are present: horizontally both tiles [1|6] and [6|1] exist, while a regular game set only has one such tile. The Unicode range for dominoes is U+1F030–U+1F09F. The naming pattern in Unicode is, by example, . Few fonts are known to support these glyphs. While the complete domino set has only 28 tiles, for printing layout reasons, the Unicode set needs both horizontal and vertical forms for each tile, plus the 01-03 (plain)
Unique key According to the SQL standard a unique constraint does not enforce uniqueness in the presence of nulls and can therefore contain several rows with identical combinations of nulls and non-null values — however not all RDBMS implement this feature according to the SQL standard. Unique key In database relational modeling and implementation, a unique key (also known as a candidate key) of a relation is a minimal superkey for that relation; that is, a set of attributes such that: When a column or set of columns is defined as unique to the database management system, the system verifies that each