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387 lines
11 KiB
Markdown
387 lines
11 KiB
Markdown
---
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slug: /en/sql-reference/functions/splitting-merging-functions
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sidebar_position: 165
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sidebar_label: Splitting Strings
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---
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# Functions for Splitting Strings
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## splitByChar
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Splits a string into substrings separated by a specified character. Uses a constant string `separator` which consists of exactly one character.
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Returns an array of selected substrings. Empty substrings may be selected if the separator occurs at the beginning or end of the string, or if there are multiple consecutive separators.
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**Syntax**
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``` sql
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splitByChar(separator, s[, max_substrings]))
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```
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**Arguments**
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- `separator` — The separator which should contain exactly one character. [String](../../sql-reference/data-types/string.md).
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- `s` — The string to split. [String](../../sql-reference/data-types/string.md).
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- `max_substrings` — An optional `Int64` defaulting to 0. When `max_substrings` > 0, the returned substrings will be no more than `max_substrings`, otherwise the function will return as many substrings as possible.
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**Returned value(s)**
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Returns an array of selected substrings. Empty substrings may be selected when:
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- A separator occurs at the beginning or end of the string;
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- There are multiple consecutive separators;
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- The original string `s` is empty.
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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**Example**
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``` sql
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SELECT splitByChar(',', '1,2,3,abcde');
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```
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Result:
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``` text
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┌─splitByChar(',', '1,2,3,abcde')─┐
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│ ['1','2','3','abcde'] │
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└─────────────────────────────────┘
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```
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## splitByString
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Splits a string into substrings separated by a string. It uses a constant string `separator` of multiple characters as the separator. If the string `separator` is empty, it will split the string `s` into an array of single characters.
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**Syntax**
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``` sql
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splitByString(separator, s[, max_substrings]))
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```
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**Arguments**
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- `separator` — The separator. [String](../../sql-reference/data-types/string.md).
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- `s` — The string to split. [String](../../sql-reference/data-types/string.md).
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- `max_substrings` — An optional `Int64` defaulting to 0. When `max_substrings` > 0, the returned substrings will be no more than `max_substrings`, otherwise the function will return as many substrings as possible.
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**Returned value(s)**
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Returns an array of selected substrings. Empty substrings may be selected when:
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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- A non-empty separator occurs at the beginning or end of the string;
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- There are multiple consecutive non-empty separators;
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- The original string `s` is empty while the separator is not empty.
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**Example**
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``` sql
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SELECT splitByString(', ', '1, 2 3, 4,5, abcde');
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```
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Result:
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``` text
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┌─splitByString(', ', '1, 2 3, 4,5, abcde')─┐
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│ ['1','2 3','4,5','abcde'] │
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└───────────────────────────────────────────┘
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```
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``` sql
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SELECT splitByString('', 'abcde');
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```
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Result:
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``` text
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┌─splitByString('', 'abcde')─┐
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│ ['a','b','c','d','e'] │
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└────────────────────────────┘
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```
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## splitByRegexp
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Splits a string into substrings separated by a regular expression. It uses a regular expression string `regexp` as the separator. If the `regexp` is empty, it will split the string `s` into an array of single characters. If no match is found for this regular expression, the string `s` won't be split.
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**Syntax**
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``` sql
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splitByRegexp(regexp, s[, max_substrings]))
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```
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**Arguments**
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- `regexp` — Regular expression. Constant. [String](../data-types/string.md) or [FixedString](../data-types/fixedstring.md).
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- `s` — The string to split. [String](../../sql-reference/data-types/string.md).
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- `max_substrings` — An optional `Int64` defaulting to 0. When `max_substrings` > 0, the returned substrings will be no more than `max_substrings`, otherwise the function will return as many substrings as possible.
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**Returned value(s)**
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Returns an array of selected substrings. Empty substrings may be selected when:
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- A non-empty regular expression match occurs at the beginning or end of the string;
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- There are multiple consecutive non-empty regular expression matches;
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- The original string `s` is empty while the regular expression is not empty.
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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**Example**
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``` sql
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SELECT splitByRegexp('\\d+', 'a12bc23de345f');
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```
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Result:
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``` text
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┌─splitByRegexp('\\d+', 'a12bc23de345f')─┐
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│ ['a','bc','de','f'] │
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└────────────────────────────────────────┘
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```
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``` sql
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SELECT splitByRegexp('', 'abcde');
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```
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Result:
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``` text
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┌─splitByRegexp('', 'abcde')─┐
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│ ['a','b','c','d','e'] │
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└────────────────────────────┘
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```
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## splitByWhitespace
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Splits a string into substrings separated by whitespace characters.
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Returns an array of selected substrings.
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**Syntax**
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``` sql
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splitByWhitespace(s[, max_substrings]))
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```
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**Arguments**
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- `s` — The string to split. [String](../../sql-reference/data-types/string.md).
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- `max_substrings` — An optional `Int64` defaulting to 0. When `max_substrings` > 0, the returned substrings will be no more than `max_substrings`, otherwise the function will return as many substrings as possible.
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**Returned value(s)**
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Returns an array of selected substrings.
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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**Example**
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``` sql
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SELECT splitByWhitespace(' 1! a, b. ');
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```
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Result:
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``` text
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┌─splitByWhitespace(' 1! a, b. ')─┐
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│ ['1!','a,','b.'] │
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└─────────────────────────────────────┘
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```
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## splitByNonAlpha
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Splits a string into substrings separated by whitespace and punctuation characters.
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Returns an array of selected substrings.
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**Syntax**
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``` sql
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splitByNonAlpha(s[, max_substrings]))
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```
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**Arguments**
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- `s` — The string to split. [String](../../sql-reference/data-types/string.md).
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- `max_substrings` — An optional `Int64` defaulting to 0. When `max_substrings` > 0, the returned substrings will be no more than `max_substrings`, otherwise the function will return as many substrings as possible.
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**Returned value(s)**
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Returns an array of selected substrings.
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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**Example**
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``` sql
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SELECT splitByNonAlpha(' 1! a, b. ');
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```
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``` text
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┌─splitByNonAlpha(' 1! a, b. ')─┐
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│ ['1','a','b'] │
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└───────────────────────────────────┘
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```
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## arrayStringConcat
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Concatenates string representations of values listed in the array with the separator. `separator` is an optional parameter: a constant string, set to an empty string by default.
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Returns the string.
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**Syntax**
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```sql
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arrayStringConcat(arr\[, separator\])
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```
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**Example**
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``` sql
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SELECT arrayStringConcat(['12/05/2021', '12:50:00'], ' ') AS DateString;
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```
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Result:
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```text
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┌─DateString──────────┐
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│ 12/05/2021 12:50:00 │
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└─────────────────────┘
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```
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## alphaTokens
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Selects substrings of consecutive bytes from the ranges a-z and A-Z.Returns an array of substrings.
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**Syntax**
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``` sql
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alphaTokens(s[, max_substrings]))
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```
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Alias: `splitByAlpha`
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**Arguments**
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- `s` — The string to split. [String](../../sql-reference/data-types/string.md).
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- `max_substrings` — An optional `Int64` defaulting to 0. When `max_substrings` > 0, the returned substrings will be no more than `max_substrings`, otherwise the function will return as many substrings as possible.
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**Returned value(s)**
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Returns an array of selected substrings.
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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**Example**
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``` sql
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SELECT alphaTokens('abca1abc');
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```
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``` text
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┌─alphaTokens('abca1abc')─┐
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│ ['abca','abc'] │
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└─────────────────────────┘
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```
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## extractAllGroups
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Extracts all groups from non-overlapping substrings matched by a regular expression.
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**Syntax**
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``` sql
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extractAllGroups(text, regexp)
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```
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**Arguments**
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- `text` — [String](../data-types/string.md) or [FixedString](../data-types/fixedstring.md).
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- `regexp` — Regular expression. Constant. [String](../data-types/string.md) or [FixedString](../data-types/fixedstring.md).
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**Returned values**
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- If the function finds at least one matching group, it returns `Array(Array(String))` column, clustered by group_id (1 to N, where N is number of capturing groups in `regexp`).
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- If there is no matching group, returns an empty array.
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Type: [Array](../data-types/array.md).
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**Example**
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``` sql
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SELECT extractAllGroups('abc=123, 8="hkl"', '("[^"]+"|\\w+)=("[^"]+"|\\w+)');
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```
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Result:
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``` text
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┌─extractAllGroups('abc=123, 8="hkl"', '("[^"]+"|\\w+)=("[^"]+"|\\w+)')─┐
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│ [['abc','123'],['8','"hkl"']] │
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└───────────────────────────────────────────────────────────────────────┘
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```
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## ngrams
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Splits a UTF-8 string into n-grams of `ngramsize` symbols.
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**Syntax**
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``` sql
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ngrams(string, ngramsize)
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```
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**Arguments**
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- `string` — String. [String](../../sql-reference/data-types/string.md) or [FixedString](../../sql-reference/data-types/fixedstring.md).
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- `ngramsize` — The size of an n-gram. [UInt](../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- Array with n-grams.
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Type: [Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md)).
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**Example**
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``` sql
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SELECT ngrams('ClickHouse', 3);
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```
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Result:
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``` text
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┌─ngrams('ClickHouse', 3)───────────────────────────┐
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│ ['Cli','lic','ick','ckH','kHo','Hou','ous','use'] │
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└───────────────────────────────────────────────────┘
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```
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## tokens
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Splits a string into tokens using non-alphanumeric ASCII characters as separators.
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**Arguments**
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- `input_string` — Any set of bytes represented as the [String](../../sql-reference/data-types/string.md) data type object.
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**Returned value**
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- The resulting array of tokens from input string.
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Type: [Array](../data-types/array.md).
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**Example**
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``` sql
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SELECT tokens('test1,;\\ test2,;\\ test3,;\\ test4') AS tokens;
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```
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Result:
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``` text
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┌─tokens────────────────────────────┐
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│ ['test1','test2','test3','test4'] │
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└───────────────────────────────────┘
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```
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