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336 lines
9.9 KiB
Markdown
336 lines
9.9 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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## overlay
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Replace part of the string `input` with another string `replace`, starting at the 1-based index `offset`.
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**Syntax**
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```sql
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overlay(s, replace, offset[, length])
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```
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**Parameters**
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- `s`: A string type [String](../data-types/string.md).
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- `replace`: A string type [String](../data-types/string.md).
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- `offset`: An integer type [Int](../data-types/int-uint.md) (1-based). If `offset` is negative, it is counted from the end of the string `s`.
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- `length`: Optional. An integer type [Int](../data-types/int-uint.md). `length` specifies the length of the snippet within the input string `s` to be replaced. If `length` is not specified, the number of bytes removed from `s` equals the length of `replace`; otherwise `length` bytes are removed.
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**Returned value**
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- A [String](../data-types/string.md) data type value.
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**Example**
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```sql
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SELECT overlay('My father is from Mexico.', 'mother', 4) 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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│ My mother is from Mexico.│
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└──────────────────────────┘
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```
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```sql
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SELECT overlay('My father is from Mexico.', 'dad', 4, 6) 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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│ My dad is from Mexico.│
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└───────────────────────┘
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```
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## overlayUTF8
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Replace part of the string `input` with another string `replace`, starting at the 1-based index `offset`.
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Assumes that the string contains valid UTF-8 encoded text.
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If this assumption is violated, no exception is thrown and the result is undefined.
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**Syntax**
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```sql
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overlayUTF8(s, replace, offset[, length])
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```
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**Parameters**
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- `s`: A string type [String](../data-types/string.md).
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- `replace`: A string type [String](../data-types/string.md).
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- `offset`: An integer type [Int](../data-types/int-uint.md) (1-based). If `offset` is negative, it is counted from the end of the input string `s`.
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- `length`: Optional. An integer type [Int](../data-types/int-uint.md). `length` specifies the length of the snippet within the input string `s` to be replaced. If `length` is not specified, the number of characters removed from `s` equals the length of `replace`; otherwise `length` characters are removed.
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**Returned value**
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- A [String](../data-types/string.md) data type value.
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**Example**
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```sql
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SELECT overlay('Mein Vater ist aus Österreich.', 'der Türkei', 20) 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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│ Mein Vater ist aus der Türkei.│
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└───────────────────────────────┘
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```
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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 contain 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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## format
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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).
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**Syntax**
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```sql
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format(pattern, s0, s1, ...)
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```
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**Example**
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``` sql
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SELECT format('{1} {0} {1}', 'World', 'Hello')
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```
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```result
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┌─format('{1} {0} {1}', 'World', 'Hello')─┐
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│ Hello World Hello │
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└─────────────────────────────────────────┘
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```
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With implicit numbers:
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``` sql
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SELECT format('{} {}', 'Hello', 'World')
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```
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```result
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┌─format('{} {}', 'Hello', 'World')─┐
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│ Hello World │
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└───────────────────────────────────┘
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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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**Syntax**
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``` sql
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translateUTF8(s, from, to)
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```
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**Parameters**
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- `s`: A string type [String](../data-types/string.md).
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- `from`: A string type [String](../data-types/string.md).
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- `to`: A string type [String](../data-types/string.md).
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**Returned value**
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- A [String](../data-types/string.md) data type value.
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**Examples**
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Query:
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``` sql
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SELECT translateUTF8('Münchener Straße', 'üß', 'us') AS res;
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```
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``` response
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┌─res──────────────┐
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│ Munchener Strase │
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└──────────────────┘
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```
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## printf
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The `printf` function formats the given string with the values (strings, integers, floating-points etc.) listed in the arguments, similar to printf function in C++. The format string can contain format specifiers starting with `%` character. Anything not contained in `%` and the following format specifier is considered literal text and copied verbatim into the output. Literal `%` character can be escaped by `%%`.
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**Syntax**
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``` sql
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printf(format, arg1, arg2, ...)
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```
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**Example**
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Query:
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``` sql
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select printf('%%%s %s %d', 'Hello', 'World', 2024);
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```
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``` response
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┌─printf('%%%s %s %d', 'Hello', 'World', 2024)─┐
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│ %Hello World 2024 │
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└──────────────────────────────────────────────┘
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```
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