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162 lines
4.7 KiB
Markdown
162 lines
4.7 KiB
Markdown
---
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slug: /en/sql-reference/functions/string-replace-functions
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sidebar_position: 150
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sidebar_label: Replacing in Strings
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---
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# Functions for Replacing in Strings
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[General strings functions](string-functions.md) and [functions for searching in strings](string-search-functions.md) are described separately.
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## replaceOne
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Replaces the first occurrence of the substring `pattern` in `haystack` by the `replacement` string.
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**Syntax**
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```sql
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replaceOne(haystack, pattern, replacement)
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```
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## replaceAll
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Replaces all occurrences of the substring `pattern` in `haystack` by the `replacement` string.
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**Syntax**
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```sql
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replaceAll(haystack, pattern, replacement)
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```
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Alias: `replace`.
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## replaceRegexpOne
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Replaces the first occurrence of the substring matching the regular expression `pattern` (in [re2 syntax](https://github.com/google/re2/wiki/Syntax)) in `haystack` by the `replacement` string.
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`replacement` can containing substitutions `\0-\9`.
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Substitutions `\1-\9` correspond to the 1st to 9th capturing group (submatch), substitution `\0` corresponds to the entire match.
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To use a verbatim `\` character in the `pattern` or `replacement` strings, escape it using `\`.
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Also keep in mind that string literals require extra escaping.
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**Syntax**
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```sql
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replaceRegexpOne(haystack, pattern, replacement)
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```
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**Example**
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Converting ISO dates to American format:
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``` sql
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SELECT DISTINCT
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EventDate,
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replaceRegexpOne(toString(EventDate), '(\\d{4})-(\\d{2})-(\\d{2})', '\\2/\\3/\\1') AS res
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FROM test.hits
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LIMIT 7
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FORMAT TabSeparated
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```
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Result:
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``` text
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2014-03-17 03/17/2014
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2014-03-18 03/18/2014
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2014-03-19 03/19/2014
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2014-03-20 03/20/2014
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2014-03-21 03/21/2014
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2014-03-22 03/22/2014
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2014-03-23 03/23/2014
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```
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Copying a string ten times:
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``` sql
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SELECT replaceRegexpOne('Hello, World!', '.*', '\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0') AS res
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```
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Result:
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``` text
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┌─res────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World!Hello, World! │
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└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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## replaceRegexpAll
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Like `replaceRegexpOne` but replaces all occurrences of the pattern.
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Alias: `REGEXP_REPLACE`.
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**Example**
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``` sql
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SELECT replaceRegexpAll('Hello, World!', '.', '\\0\\0') AS res
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```
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Result:
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``` text
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┌─res────────────────────────┐
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│ HHeelllloo,, WWoorrlldd!! │
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└────────────────────────────┘
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```
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As an exception, if a regular expression worked on an empty substring, the replacement is not made more than once, e.g.:
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``` sql
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SELECT replaceRegexpAll('Hello, World!', '^', 'here: ') AS res
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```
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Result:
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``` text
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┌─res─────────────────┐
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│ here: Hello, World! │
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└─────────────────────┘
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```
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## regexpQuoteMeta
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Adds a backslash before these characters with special meaning in regular expressions: `\0`, `\\`, `|`, `(`, `)`, `^`, `$`, `.`, `[`, `]`, `?`, `*`, `+`, `{`, `:`, `-`.
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This implementation slightly differs from re2::RE2::QuoteMeta. It escapes zero byte as `\0` instead of `\x00` and it escapes only required characters.
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For more information, see [RE2](https://github.com/google/re2/blob/master/re2/re2.cc#L473)
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**Syntax**
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```sql
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regexpQuoteMeta(s)
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```
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## translate
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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.
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**Syntax**
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```sql
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translate(s, from, to)
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```
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**Example**
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``` sql
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SELECT translate('Hello, World!', 'delor', 'DELOR') AS res
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```
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Result:
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``` text
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┌─res───────────┐
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│ HELLO, WORLD! │
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└───────────────┘
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```
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## translateUTF8
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Like [translate](#translate) but assumes `s`, `from` and `to` are UTF-8 encoded strings.
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