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Constants in Azure Cosmos DB for NoSQL

  • บทความ

APPLIES TO: NoSQL

A constant, also known as a literal or a scalar value, is a symbol that represents a specific data value. The format of a constant depends on the data type of the value it represents.

Syntax

<constant> ::=  
   <undefined_constant>  
     | <null_constant>   
     | <boolean_constant>   
     | <number_constant>   
     | <string_constant>   
     | <array_constant>   
     | <object_constant>   
  
<undefined_constant> ::= undefined  
  
<null_constant> ::= null  
  
<boolean_constant> ::= false | true  
  
<number_constant> ::= decimal_literal | hexadecimal_literal  
  
<string_constant> ::= string_literal  
  
<array_constant> ::=  
    '[' [<constant>][,...n] ']'  
  
<object_constant> ::=   
   '{' [{property_name | "property_name"} : <constant>][,...n] '}'

Arguments

Description
<undefined_constant>; Undefined Represents undefined values of type Undefined.
<null_constant>; null Represents null values of type Null.
<boolean_constant> Represents boolean-typed constants.
false Represents false value of type boolean.
true Represents true value of type boolean.
<number_constant> Represents a numeric constant.
decimal_literal Numbers represented using either decimal notation, or scientific notation.
hexadecimal_literal Numbers represented using prefix 0x followed by one or more hexadecimal digits.
<string_constant> Represents a constant of type string.
string _literal Unicode strings represented by a sequence of zero or more Unicode characters or escape sequences. String literals are enclosed in single quotes (apostrophe: ') or double quotes (quotation mark: ").

Remarks

  • Here's a list of the supported scalar data types:

    Values order
    Undefined Single value: undefined
    Null Single value: null
    Boolean Values: false, true.
    Number A double-precision floating-point number, IEEE 754 standard.
    String A sequence of zero or more Unicode characters. Strings must be enclosed in single or double quotes.
    Array A sequence of zero or more elements. Each element can be a value of any scalar data type, except undefined.
    Object An unordered set of zero or more name/value pairs. Name is a Unicode string, value can be of any scalar data type, except undefined.

  • Here's a list of escape sequences that are allowed for string literals:

    Description Unicode character
    \' apostrophe (') U+0027
    \" quotation mark (") U+0022
    \\ reverse solidus () U+005C
    \/ solidus (/) U+002F
    \b backspace U+0008
    \f separator feed U+000C
    \n line feed U+000A
    \r carriage return U+000D
    \t tab U+0009
    \uXXXX A Unicode character defined by four hexadecimal digits. U+XXXX

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