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  2. Null (SQL) - Wikipedia

    en.wikipedia.org/wiki/Null_(SQL)

    In SQL, NULL is a reserved word used to identify this marker. A null should not be confused with a value of 0. A null indicates a lack of a value, which is not the same as a zero value. For example, consider the question "How many books does Adam own?" The answer may be "zero" (we know that he owns none) or "null" (we do not know how many he owns).

  3. Null pointer - Wikipedia

    en.wikipedia.org/wiki/Null_pointer

    In computing, a null pointer or null reference is a value saved for indicating that the pointer or reference does not refer to a valid object. Programs routinely use null pointers to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types ...

  4. Null - Wikipedia

    en.wikipedia.org/wiki/Null

    Null (SQL) (or NULL), a special marker and keyword in SQL indicating that something has no value; Null character, the zero-valued ASCII character, also designated by NUL, often used as a terminator, separator or filler. This symbol has no visual representation. Null device, a virtual file that discards data written to it, on Unix systems /dev/null

  5. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    The word NULL is a reserved keyword in SQL, used to identify the Null special marker. Comparisons with Null, for instance equality (=) in WHERE clauses, results in an Unknown truth value. Comparisons with Null, for instance equality (=) in WHERE clauses, results in an Unknown truth value.

  6. Pointer (computer programming) - Wikipedia

    en.wikipedia.org/wiki/Pointer_(computer_programming)

    A null pointer has a value reserved for indicating that the pointer does not refer to a valid object. Null pointers are routinely used to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the Nothing value in an option type.

  7. SQL - Wikipedia

    en.wikipedia.org/wiki/SQL

    The concept of Null is the subject of some debate. The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the 3-valued-logic in SQL, which is a concrete implementation of the general 3-valued logic. [12]

  8. List of SQL reserved words - Wikipedia

    en.wikipedia.org/wiki/List_of_SQL_reserved_words

    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 ]

  9. Null character - Wikipedia

    en.wikipedia.org/wiki/Null_character

    It is often abbreviated as NUL (or NULL, though in some contexts that term is used for the null pointer). In 8-bit codes, it is known as a null byte . The original meaning of this character was like NOP —when sent to a printer or a terminal , it has no effect (some terminals, however, incorrectly display it as space ).