This is the multi-page printable view of this section.
Click here to print.
Return to the regular view of this page.
String literals
String literals are string values surrounded by single or double quotes.
String literals are string values surrounded by single or double quotes. Double-quoted strings are subject to the backslash, but single-quoted strings do not require a backslash, except for \' and \\.
You can embed single quotes and backslashes into single-quoted strings.
To include other backslash (escape) sequences, such as \t (tab), you must use the double-quoted form.
Precede single-quoted strings with a space between the string and its preceding word, since single quotes are allowed in identifiers.
See also
1 - Character string literals
Character string literals are a sequence of characters from a predefined character set, enclosed by single quotes.
Character string literals are a sequence of characters from a predefined character set, enclosed by single quotes.
Syntax
'character-seq'
Parameters
character-seq- Arbitrary sequence of characters
Embedded single quotes
If a character string literal includes a single quote, it must be doubled. For example:
=> SELECT 'Chester''s gorilla';
?column?
-------------------
Chester's gorilla
(1 row)
Vertica uses standard-conforming strings as specified in the SQL standard, so backslashes are treated as string literals and not escape characters.
Note
Earlier versions of Vertica did not use standard conforming strings, and backslashes were always considered escape sequences. To revert to this older behavior, set the configuration parameter
StandardConformingStrings to 0. You can also use the
EscapeStringWarning parameter to locate back slashes which have been incorporated into string literals, in order to remove them.
Examples
=> SELECT 'This is a string';
?column?
------------------
This is a string
(1 row)
=> SELECT 'This \is a string';
WARNING: nonstandard use of escape in a string literal at character 8
HINT: Use the escape string syntax for escapes, e.g., E'\r\n'.
?column?
------------------
This is a string
(1 row)
vmartdb=> SELECT E'This \is a string';
?column?
------------------
This is a string
=> SELECT E'This is a \n new line';
?column?
----------------------
This is a
new line
(1 row)
=> SELECT 'String''s characters';
?column?
--------------------
String's characters
(1 row)
See also
2 - Dollar-quoted string literals
Dollar-quoted string literals are rarely used, but are provided here for your convenience.
Dollar-quoted string literals are rarely used, but are provided here for your convenience.
The standard syntax for specifying string literals can be difficult to understand. To allow more readable queries in such situations, Vertica SQL provides dollar quoting. Dollar quoting is not part of the SQL standard, but it is often a more convenient way to write complicated string literals than the standard-compliant single quote syntax.
Syntax
$$characters$$
Parameters
characters- Arbitrary sequence of characters bounded by paired dollar signs (
$$)
Dollar-quoted string content is treated as a literal. Single quote, backslash, and dollar sign characters have no special meaning within a dollar-quoted string.
Notes
A dollar-quoted string that follows a keyword or identifier must be separated from the preceding word by whitespace; otherwise, the dollar-quoting delimiter is taken as part of the preceding identifier.
Examples
=> SELECT $$Fred's\n car$$;
?column?
-------------------
Fred's\n car
(1 row)
=> SELECT 'SELECT 'fact';';
ERROR: syntax error at or near "';'" at character 21
LINE 1: SELECT 'SELECT 'fact';';
=> SELECT 'SELECT $$fact';$$;
?column?
---------------
SELECT $$fact
(1 row)
=> SELECT 'SELECT ''fact'';';
?column?
----------------
SELECT 'fact';
(1 row)
3 - Unicode string literals
hexit is hexadecimal integer (0-9, a-f).
Syntax
U&'characters' [ UESCAPE '<Unicode escape character>' ]
Parameters
characters- Arbitrary sequence of UTF-8 characters bounded by single quotes (')
Unicode escape character- A single character from the source language character set other than a hexit, plus sign (+), quote ('), double quote (''), or white space
With StandardConformingStrings enabled, Vertica supports SQL standard Unicode character string literals (the character set is UTF-8 only).
Before you enter a Unicode character string literal, enable standard conforming strings in one of the following ways.
See also Extended String Literals.
Examples
To enter a Unicode character in hexadecimal, such as the Russian phrase for "thank you, use the following syntax:
=> SET STANDARD_CONFORMING_STRINGS TO ON;
=> SELECT U&'\0441\043F\0430\0441\0438\0431\043E' as 'thank you';
thank you
-----------
спасибо
(1 row)
To enter the German word mude (where u is really u-umlaut) in hexadecimal:
=> SELECT U&'m\00fcde';
?column?
----------
müde
(1 row)
=> SELECT 'ü';
?column?
----------
ü
(1 row)
To enter the LINEAR B IDEOGRAM B240 WHEELED CHARIOT in hexadecimal:
=> SELECT E'\xF0\x90\x83\x8C';
?column?
----------
(wheeled chariot character)
(1 row)
Note
Not all fonts support the wheeled chariot character.
See also
4 - VARBINARY string literals
VARBINARY string literals allow you to specify hexadecimal or binary digits in a string literal.
VARBINARY string literals allow you to specify hexadecimal or binary digits in a string literal.
Syntax
X''
B''
Parameters
X or x- Specifies hexadecimal digits. The <hexadecimal digits> string must be enclosed in single quotes (').
B or b- Specifies binary digits. The <binary digits> string must be enclosed in single quotes (').
Examples
=> SELECT X'abcd';
?column?
----------
\253\315
(1 row)
=> SELECT B'101100';
?column?
----------
,
(1 row)
5 - Extended string literals
Syntax
E'characters'
Parameters
characters- Arbitrary sequence of characters bounded by single quotes (')
You can use C-style backslash sequence in extended string literals, which are an extension to the SQL standard. You specify an extended string literal by writing the letter E as a prefix (before the opening single quote); for example:
E'extended character string\n'
Within an extended string, the backslash character (\) starts a C-style backslash sequence, in which the combination of backslash and following character or numbers represent a special byte value, as shown in the following list. Any other character following a backslash is taken literally; for example, to include a backslash character, write two backslashes (\\).
-
\\ is a backslash
-
\b is a backspace
-
\f is a form feed
-
\n is a newline
-
\r is a carriage return
-
\t is a tab
-
\x##,where ## is a 1 or 2-digit hexadecimal number; for example \x07 is a tab
-
\###, where ### is a 1, 2, or 3-digit octal number representing a byte with the corresponding code.
When an extended string literal is concatenated across lines, write only E before the first opening quote:
=> SELECT E'first part o'
'f a long line';
?column?
---------------------------
first part of a long line
(1 row)
Two adjacent single quotes are used as one single quote:
=> SELECT 'Aren''t string literals fun?';
?column?
-----------------------------
Aren't string literals fun?
(1 row)
When interpreting commands, such as those entered in vsql or in queries passed via JDBC or ODBC, Vertica uses standard conforming strings as specified in the SQL standard. In standard conforming strings, backslashes are treated as string literals (ordinary characters), not escape characters.
Note
Text read in from files or streams (such as the data inserted using the
COPY statement) are not treated as literal strings. The COPY command defines its own escape characters for the data it reads. See the
COPY statement documentation for details.
The following options are available, but Vertica recommends that you migrate your application to use standard conforming strings at your earliest convenience, after warnings have been addressed.
-
To treat back slashes as escape characters, set configuration parameter
StandardConformingStrings to 0.
-
To enable standard conforming strings permanently, set the StandardConformingStrings parameter to '1', as described below.
-
To enable standard conforming strings per session, use SET STANDARD_CONFORMING_STRING TO ON, which treats backslashes as escape characters for the current session only.
The following procedure can be used to identify nonstandard conforming strings in your application so that you can convert them into standard conforming strings:
-
Be sure the StandardConformingStrings parameter is off, as described in Internationalization parameters.
=> ALTER DATABASE DEFAULT SET StandardConformingStrings = 0;
Note
Vertica recommends that you migrate your application to use standard conforming strings .
-
If necessary, turn on the EscapeStringWarning parameter.
=> ALTER DATABASE DEFAULT SET EscapeStringWarning = 1;
Vertica now returns a warning each time it encounters an escape string within a string literal. For example, Vertica interprets the \n in the following example as a new line:
=> SELECT 'a\nb';
WARNING: nonstandard use of escape in a string literal at character 8
HINT: Use the escape string syntax for escapes, e.g., E'\r\n'.
?column?
----------
a
b
(1 row)
When StandardConformingStrings is ON, the string is interpreted as four characters: a \ n b.
Modify each string that Vertica flags by extending it as in the following example:
E'a\nb'
Or if the string has quoted single quotes, double them; for example, 'one'' double'.
-
Turn on the StandardConformingStrings parameter for all sessions:
=> ALTER DATABASE DEFAULT SET StandardConformingStrings = 1;
Doubled single quotes
This section discusses vsql inputs that are not passed on to the server.
Vertica recognizes two consecutive single quotes within a string literal as one single quote character. For example, the following inputs, 'You''re here!' ignored the second consecutive quote and returns the following:
=> SELECT 'You''re here!';
?column?
--------------
You're here!at
(1 row)
This is the SQL standard representation and is preferred over the form, 'You\'re here!', because backslashes are not parsed as before. You need to escape the backslash:
=> SELECT (E'You\'re here!');
?column?
--------------
You're here!
(1 row)
This behavior change introduces a potential incompatibility in the use of the vsql meta-command \set, which automatically concatenates its arguments. For example:
\set file '\'' 'pwd' '/file.txt' '\''\echo :file
vsql takes the four arguments and outputs the following:
'/home/vertica/file.txt'
Vertica parses the adjacent single quotes as follows:
\set file '\'''pwd''/file.txt''\''\echo :file
'/home/vertica/file.txt''
Note the extra single quote at the end. This is due to the pair of adjacent single quotes together with the backslash-quoted single quote.
The extra quote can be resolved either as in the first example above, or by combining the literals as follows:
\set file '\''`pwd`'/file.txt'''\echo :file
'/home/vertica/file.txt'
In either case the backslash-quoted single quotes should be changed to doubled single quotes as follows:
\set file '''' `pwd` '/file.txt'''
Additional examples
=> SELECT 'This \is a string';
?column?
------------------
This \is a string
(1 row)
=> SELECT E'This \is a string';
?column?
------------------
This is a string
=> SELECT E'This is a \n new line';
?column?
----------------------
This is a
new line
(1 row)
=> SELECT 'String''s characters';
?column?
--------------------
String's characters
(1 row)