ClickHouse/docs/en/sql-reference/functions/string-replace-functions.md

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/en/sql-reference/functions/string-replace-functions	150	Replacing in Strings

Functions for Replacing in Strings

General strings functions and functions for searching in strings are described separately.

replaceOne

Replaces the first occurrence of the substring pattern in haystack by the replacement string.

Syntax

replaceOne(haystack, pattern, replacement)

replaceAll

Replaces all occurrences of the substring pattern in haystack by the replacement string.

Syntax

replaceAll(haystack, pattern, replacement)

Alias: replace.

replaceRegexpOne

Replaces the first occurrence of the substring matching the regular expression pattern (in re2 syntax) in haystack by the replacement string.

replacement can contain substitutions \0-\9. Substitutions \1-\9 correspond to the 1st to 9th capturing group (submatch), substitution \0 corresponds to the entire match.

To use a verbatim \ character in the pattern or replacement strings, escape it using \. Also keep in mind that string literals require extra escaping.

Syntax

replaceRegexpOne(haystack, pattern, replacement)

Example

Converting ISO dates to American format:

SELECT DISTINCT
    EventDate,
    replaceRegexpOne(toString(EventDate), '(\\d{4})-(\\d{2})-(\\d{2})', '\\2/\\3/\\1') AS res
FROM test.hits
LIMIT 7
FORMAT TabSeparated

Result:

2014-03-17      03/17/2014
2014-03-18      03/18/2014
2014-03-19      03/19/2014
2014-03-20      03/20/2014
2014-03-21      03/21/2014
2014-03-22      03/22/2014
2014-03-23      03/23/2014

Copying a string ten times:

SELECT replaceRegexpOne('Hello, World!', '.*', '\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0') AS res

Result:

┌─res────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World! │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

replaceRegexpAll

Like replaceRegexpOne but replaces all occurrences of the pattern.

Alias: REGEXP_REPLACE.

Example

SELECT replaceRegexpAll('Hello, World!', '.', '\\0\\0') AS res

Result:

┌─res────────────────────────┐
│ HHeelllloo,,  WWoorrlldd!! │
└────────────────────────────┘

As an exception, if a regular expression worked on an empty substring, the replacement is not made more than once, e.g.:

SELECT replaceRegexpAll('Hello, World!', '^', 'here: ') AS res

Result:

┌─res─────────────────┐
│ here: Hello, World! │
└─────────────────────┘

regexpQuoteMeta

Adds a backslash before these characters with special meaning in regular expressions: \0, \\, |, (, ), ^, $, ., [, ], ?, *, +, {, :, -.

This implementation slightly differs from re2::RE2::QuoteMeta. It escapes zero byte as \0 instead of \x00 and it escapes only required characters. For more information, see RE2

Syntax

regexpQuoteMeta(s)

format

Format the pattern string with the values (strings, integers, etc.) listed in the arguments, similar to formatting in Python. The pattern string can contain replacement fields surrounded by curly braces {}. Anything not contained in braces is considered literal text and copied verbatim into the output. Literal brace character can be escaped by two braces: {{ '{{' }} and {{ '}}' }}. Field names can be numbers (starting from zero) or empty (then they are implicitly given monotonically increasing numbers).

Syntax

format(pattern, s0, s1, ...)

Example

SELECT format('{1} {0} {1}', 'World', 'Hello')

┌─format('{1} {0} {1}', 'World', 'Hello')─┐
│ Hello World Hello                       │
└─────────────────────────────────────────┘

With implicit numbers:

SELECT format('{} {}', 'Hello', 'World')

┌─format('{} {}', 'Hello', 'World')─┐
│ Hello World                       │
└───────────────────────────────────┘

translate

Replaces characters in the string s using a one-to-one character mapping defined by from and to strings. from and to must be constant ASCII strings of the same size. Non-ASCII characters in the original string are not modified.

Syntax

translate(s, from, to)

Example

SELECT translate('Hello, World!', 'delor', 'DELOR') AS res

Result:

┌─res───────────┐
│ HELLO, WORLD! │
└───────────────┘

translateUTF8

Like translate but assumes s, from and to are UTF-8 encoded strings.

Syntax

translateUTF8(s, from, to)

Parameters

• s: A string type String.
• from: A string type String.
• to: A string type String.

Returned value

• A String data type value.

Examples

Query:

SELECT translateUTF8('Münchener Straße', 'üß', 'us') AS res;

┌─res──────────────┐
│ Munchener Strase │
└──────────────────┘