mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-18 04:12:19 +00:00
162 lines
4.7 KiB
Markdown
162 lines
4.7 KiB
Markdown
---
|
|
slug: /en/sql-reference/functions/string-replace-functions
|
|
sidebar_position: 150
|
|
sidebar_label: Replacing in Strings
|
|
---
|
|
|
|
# Functions for Replacing in Strings
|
|
|
|
[General strings functions](string-functions.md) and [functions for searching in strings](string-search-functions.md) are described separately.
|
|
|
|
## replaceOne
|
|
|
|
Replaces the first occurrence of the substring `pattern` in `haystack` by the `replacement` string.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
replaceOne(haystack, pattern, replacement)
|
|
```
|
|
|
|
## replaceAll
|
|
|
|
Replaces all occurrences of the substring `pattern` in `haystack` by the `replacement` string.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
replaceAll(haystack, pattern, replacement)
|
|
```
|
|
|
|
Alias: `replace`.
|
|
|
|
## replaceRegexpOne
|
|
|
|
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.
|
|
|
|
`replacement` can 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` strings, escape it using `\`.
|
|
Also keep in mind that string literals require extra escaping.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
replaceRegexpOne(haystack, pattern, replacement)
|
|
```
|
|
|
|
**Example**
|
|
|
|
Converting ISO dates to American format:
|
|
|
|
``` sql
|
|
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:
|
|
|
|
``` text
|
|
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:
|
|
|
|
``` sql
|
|
SELECT replaceRegexpOne('Hello, World!', '.*', '\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0') AS res
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─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**
|
|
|
|
``` sql
|
|
SELECT replaceRegexpAll('Hello, World!', '.', '\\0\\0') AS res
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─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.:
|
|
|
|
``` sql
|
|
SELECT replaceRegexpAll('Hello, World!', '^', 'here: ') AS res
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─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](https://github.com/google/re2/blob/master/re2/re2.cc#L473)
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
regexpQuoteMeta(s)
|
|
```
|
|
|
|
## 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**
|
|
|
|
```sql
|
|
translate(s, from, to)
|
|
```
|
|
|
|
**Example**
|
|
|
|
``` sql
|
|
SELECT translate('Hello, World!', 'delor', 'DELOR') AS res
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─res───────────┐
|
|
│ HELLO, WORLD! │
|
|
└───────────────┘
|
|
```
|
|
|
|
## translateUTF8
|
|
|
|
Like [translate](#translate) but assumes `s`, `from` and `to` are UTF-8 encoded strings.
|