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

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/en/sql-reference/functions/string-replace-functions	42	Replacing in Strings

Functions for Searching and Replacing in Strings

:::note Functions for searching and other manipulations with strings are described separately. :::

replaceOne(haystack, pattern, replacement)

Replaces the first occurrence of the substring ‘pattern’ (if it exists) in ‘haystack’ by the ‘replacement’ string.

replaceAll(haystack, pattern, replacement), replace(haystack, pattern, replacement)

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

Alias: replace.

replaceRegexpOne(haystack, pattern, replacement)

Replaces the first occurrence of the substring matching the regular expression ‘pattern’ in ‘haystack‘ by the ‘replacement‘ string. ‘pattern‘ must be a re2 regular expression. ‘replacement’ must be a plain string or a string containing 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‘ string, escape it using \. Also keep in mind that string literals require an extra escaping.

Example 1. 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

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

Example 2. Copying a string ten times:

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

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

replaceRegexpAll(haystack, pattern, replacement)

Like ‘replaceRegexpOne‘, but replaces all occurrences of the pattern. Example:

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

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

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

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

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

Alias: REGEXP_REPLACE.

regexpQuoteMeta(s)

The function adds a backslash before some predefined characters in the string. Predefined characters: \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 the link: RE2

translate(s, from, to)

The function replaces characters in the string ‘s’ in accordance with 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.

Example:

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

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

translateUTF8(string, from, to)

Similar to previous function, but works with UTF-8 arguments. ‘from’ and ‘to’ must be valid constant UTF-8 strings of the same size.

Example:

SELECT translateUTF8('Hélló, Wórld¡', 'óé¡', 'oe!') AS res

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