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XQuery by Priscilla Walmsley

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XML Entity and Character References

Like XML, the XQuery syntax allows for the escaping of individual characters using two mechanisms: character references and predefined entity references. These escapes can be used in string literals, as well as in the content of direct element and attribute constructors.

Character references are useful for representing characters that are not easily typed on a keyboard. They take two forms:

  • &# plus a sequence of decimal digits representing the character's code point, followed by a semicolon (;).

  • &#x plus a sequence of hexadecimal digits representing the character's code point, followed by a semicolon (;).

For example, a space can be represented as   or  . The number always refers to the Unicode code point; it doesn't depend on the query encoding. Table 21-1 lists a few common XML character references.

Table 21-1. XML character reference examples

Character reference

Meaning

 

Space




Line feed



Carriage return

	

Tab

Predefined entity references are useful for escaping characters that have special meaning in XML syntax. They are listed in Table 21-2.

Table 21-2. Predefined entity references

Entity reference

Meaning

&

Ampersand (&)

<

Less than (<)

&gt;

Greater than (>)

&apos;

Apostrophe/single quote (')

&quot;

Double quote (")

Certain of these characters must be escaped, namely:

  • In literal strings, ampersands, as well as single or double quotes (depending on which was used ...

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