The string data type

• 02/13/2020
• 2 minutes to read

In this article

The string data type represents a Unicode string. Kusto strings are encoded in UTF-8 and by default are limited to 1MB.

String literals

There are several ways to encode literals of the string data type.

• Enclose the string in double-quotes ("): "This is a string literal. Single quote characters (') don't require escaping. Double quote characters (\") are escaped by a backslash (\\)"
• Enclose the string in single-quotes ('): 'Another string literal. Single quote characters (\') require escaping by a backslash (\\). Double quote characters (") do not require escaping.'

In the two representations above, the backslash (\) character indicates escaping. It's used to escape the enclosing quote characters, tab characters (\t), newline characters (\n), and itself (\\).

Verbatim string literals are also supported. In this form, the backslash character (\) stands for itself, and not as an escape character.

• Enclose in double-quotes ("): @"This is a verbatim string literal that ends with a backslash\"
• Enclose in single-quotes ('): @'This is a verbatim string literal that ends with a backslash\'

Two string literals in the query with nothing between them, or separated only by whitespace and comments, automatically join to form a new string literal. For example, the following expressions all yield length 13.

print strlen("Hello"', '@"world!"); // Nothing between them

print strlen("Hello" ', ' @"world!"); // Separated by whitespace only

print strlen("Hello"
  // Comment
  ', '@"world!"); // Separated by whitespace and a comment

Examples

// Simple string notation
print s1 = 'some string', s2 = "some other string"

// Strings that include single or double-quotes can be defined as follows
print s1 = 'string with " (double quotes)',
          s2 = "string with ' (single quotes)"

// Strings with '\' can be prefixed with '@' (as in c#)
print myPath1 = @'C:\Folder\filename.txt'

// Escaping using '\' notation
print s = '\\n.*(>|\'|=|\")[a-zA-Z0-9/+]{86}=='

As can be seen, when a string is enclosed in double-quotes ("), the single-quote (') character doesn't require escaping, and also the other way around. This method makes it easier to quote strings according to context.

Obfuscated string literals

The system tracks queries and stores them for telemetry and analysis purposes. For example, the query text might be made available to the cluster owner. If the query text includes secret information, such as passwords, it might leak information that should be kept private. To prevent such a leak from happening, the query author may mark specific string literals as obfuscated string literals. Such literals in the query text are automatically replaced by a number of star (*) characters, so that they aren't available for later analysis.

An obfuscated string literal can be formed by taking a "regular" string literal, and prepending an h or an H character in front of it.

For example:

h'hello'
h@'world'
h"hello"

For example:

print x="https://contoso.blob.core.windows.net/container/blob.txt?"
  h'sv=2012-02-12&se=2013-04-13T0...'