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Subject: 4.1. Lexical Structure
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Date: Thu, 27 Aug 2026 05:14:33 +0000
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The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/18/sql-syntax-lexical.html
Description:

Why repeat information within the same section?

In Section 4.1.1, =E2=80=9CIdentifiers and Keywords=E2=80=9D:

>> The option with identifiers in quotation marks allows you to include
escaped Unicode characters identified by their code points. This option
begins with U& (an uppercase or lowercase U followed by an ampersand)
immediately before the opening double quotation mark, with no spaces between
them, for example, U&=E2=80=9Cfoo=E2=80=9D. (Note that this creates ambigui=
ty regarding the
& operator. To avoid this problem, use spaces around the operator.) Inside
the quotation marks, Unicode characters can be specified in escaped form by
writing a backslash followed by the character=E2=80=99s four-digit hexadeci=
mal code,
or, alternatively, a backslash followed by a plus sign, followed by the
character=E2=80=99s six-digit hexadecimal code. For example, the identifier=
 =E2=80=9Cdata=E2=80=9D
can be written as follows:

> U&=E2=80=9Cd\0061t\+000061=E2=80=9D
...
....

This information, along with examples, is also provided in Section 4.1.2.3.
String Constants with Escaped Unicode Characters

>> PostgreSQL also supports another type of string escape syntax that allows
you to specify arbitrary Unicode characters by code point. A Unicode-escaped
string constant begins with U& (an uppercase or lowercase U followed by an
ampersand) immediately before the opening quote, with no spaces between
them, for example, U&=E2=80=9Cfoo=E2=80=9D. (Note that this creates ambigui=
ty with the &
operator. To avoid this problem, use spaces around the operator.) Inside the
quotes, Unicode characters can be specified in escaped form by writing a
backslash followed by the four-digit hexadecimal code of the character, or,
alternatively, a backslash followed by a plus sign, followed by the
six-digit hexadecimal code of the character. For example, the string =E2=80=
=9Cdata=E2=80=9D
can be written as follows:

> U&'d\0061t\+000061'
...
....