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Under Windows, the Alt key is pressed and held down while a decimal character code is entered on the numeric keypad; the Alt key is then released and the character appears. The numerical code corresponds to the character’s code point in the Windows 1252 code page, with a leading zero; for example, an en dash (–) is entered using Alt+0150 ...
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 typically used to join multiple tables.
This did not work for characters not in the Windows Code Page (such as box-drawing characters). The new Alt+0### combination (which prefixes a zero to each Alt code), produces characters from the newer "Windows code pages." [a] For example, Alt+ 0 1 6 3 yields the character £ (symbol for the pound sterling) which is at 163 in CP1252. [2] [b]
A numeric character reference refers to a character by its Universal Character Set/Unicode code point, and a character entity reference refers to a character by a predefined name. A numeric character reference uses the format &#nnnn; or &#xhhhh; where nnnn is the code point in decimal form, and hhhh is the code point in hexadecimal form.
special characters that are not available in the limited character set are stored in the form of a multi-character code; there are usually two or three equivalent representations, e.g. for the character € the named character reference € and the decimal character reference € and the hexadecimal character reference €. The edit ...
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 ...
Some modern text file formats (e.g. CSV-1203 [10]) still recommend a trailing EOF character to be appended as the last character in the file. However, typing Control+Z does not embed an EOF character into a file in either DOS or Windows, nor do the APIs of those systems use the character to denote the actual end of a file.
This page lists codes for keyboard characters, the computer code values for common characters, such as the Unicode or HTML entity codes (see below: Table of HTML values"). There are also key chord combinations, such as keying an en dash ('–') by holding ALT+0150 on the numeric keypad of MS Windows computers.