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NULL    音标拼音: [n'ʌl]
n. 空,零迅号,零
a. 无效力的,无效的,无价值的

空,零迅号,零无效力的,无效的,无价值的

null
空的; 空; 无; 零; 空白; 虚字; 空( 字元 ) NUL

null
空

null
adj 1: lacking any legal or binding force; "null and void" [synonym:
{null}, {void}]
n 1: a quantity of no importance; "it looked like nothing I had
ever seen before"; "reduced to nil all the work we had
done"; "we racked up a pathetic goose egg"; "it was all for
naught"; "I didn't hear zilch about it" [synonym: {nothing},
{nil}, {nix}, {nada}, {null}, {aught}, {cipher}, {cypher},
{goose egg}, {naught}, {zero}, {zilch}, {zip}, {zippo}]

Null \Null\, v. t. [From null, a., or perh. abbrev. from annul.]
To annul. [Obs.] --Milton.
[1913 Webster]


Null \Null\, n. [Etymol. uncertain.]
One of the beads in {nulled work}.
[1913 Webster]


Null \Null\, a. [L. nullus not any, none; ne not ullus any, a
dim. of unus one; cf. F. nul. See {No}, and {One}, and cf.
{None}.]
1. Of no legal or binding force or validity; of no efficacy;
invalid; void; nugatory; useless.
[1913 Webster]

Faultily faultless, icily regular, splendidly null,
Dead perfection; no more. --Tennyson.
[1913 Webster]

2. Having a value of zero; as, of null utility.
[PJC]

3. (Math.) Empty; having no members; as, the null set.
[PJC]

4. (Computers) Unassigned or meaningless; -- a special value
given to variables, especially pointers or logical
variables, indicating that it is meaningless and cannot be
used in computation; as, an uninitialized pointer in "C"
is given a null value. The actual value that is stored in
memory to indicate the null condition may vary with the
computer language used.
[PJC]


Null \Null\, n.
1. Something that has no force or meaning.
[1913 Webster]

2. That which has no value; a cipher; zero. --Bacon.
[1913 Webster]

{Null method} (Physics.), a zero method. See under {Zero}.
[1913 Webster]

51 Moby Thesaurus words for "null":
aimless, bad, bare, barren, bland, blank, bleached, characterless,
clear, designless, devoid, empty, existless, featureless, garbled,
hollow, importless, inane, ineffective, ineffectual, inefficacious,
insignificant, insipid, invalid, lacking, meaningless, minus,
missing, negative, nonconnotative, nondenotative, nonexistent,
null and void, phatic, purportless, purposeless, scrambled,
senseless, unexisting, unmeaning, unrelieved, unsignificant,
useless, vacant, vacuous, void, white, with nothing inside,
without being, without content, worthless

A special value used in several languages to
represent the thing referred to by an uninitialised pointer.

A special value that may be stored in some database
columns to represent an unknown, missing, not applicable, or
undefined value. Nulls are treated completely differently
from ordinary values when evaluating SQL expressions and there
are several SQL constructs for dealing with nulls.

(2003-06-17)


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英文字典中文字典相关资料:


  • c# - What does null! statement mean? - Stack Overflow
    It can be used on a type to control Nullability, it is then called the "Null Forgiving Operator" Basically, null! applies the ! operator to the value null This overrides the nullability of the value null to non-nullable, telling the compiler that null is a "non-null" type
  • Why does NULL = NULL evaluate to false in SQL server
    The expression "NULL = NULL" evaluates to NULL, but is actually invalid in SQL; yet ORDER BY treats NULLs as equal (whatever they precede or follow "regular" values is left to DBMS vendor)
  • What is the difference between is not null and != null?
    The main difference between e != null and e is not null is the way the the compiler executes the comparison Microsoft: "The compiler guarantees that no user-overloaded equality operator == is invoked when expression x is null is evaluated " Bottom Line: If you are writing code that you don't want to depend on someone's implementation of the != and == operators, use is null and is not null
  • javascript - Why is null an object and whats the difference between . . .
    In order to be able to query this difference, JavaScript has null and undefined: While null is - just like in other languages an object, undefined cannot be an object because there is no instance (even not a null instance) available
  • What is the difference between NULL, \0 and 0? - Stack Overflow
    In C, there appear to be differences between various values of zero -- NULL, NUL and 0 I know that the ASCII character '0' evaluates to 48 or 0x30 The NULL pointer is usually defined as: #define
  • sql - Not equal lt; gt; != operator on NULL - Stack Overflow
    135 NULL has no value, and so cannot be compared using the scalar value operators In other words, no value can ever be equal to (or not equal to) NULL because NULL has no value Hence, SQL has special IS NULL and IS NOT NULL predicates for dealing with NULL
  • What is the purpose of null? - Stack Overflow
    Null: The Billion Dollar Mistake Tony Hoare: I call it my billion-dollar mistake It was the invention of the null reference in 1965 At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W) My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler But I
  • c# - Math operations with null - Stack Overflow
    The operators for Nullable<T> are so-called "lifted" operators]; the c# compiler takes the operators available for T and applies a set of pre-defined rules; for example, with +, the lifted + is null if either operand is null, else the sum of the inner values Re the last; again, division is defined as null if either operand is null - it never performs the division
  • How to send NULL in HTTP query string? - Stack Overflow
    So if you don't need to support the difference between empty and null absent string you may also consider the empty parameter as null If instead you want to recreate point 4 of JSON {"param":null} with request parameters you must use a convention, like passing %00 as suggested in the answers or using the null marker parameter I propose later
  • JavaScript checking for null vs. undefined and difference between . . .
    How do I check a variable if it's null or undefined and what is the difference between the null and undefined? What is the difference between == and === (it's hard to search Google for "===" )?





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