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154 lines
4.9 KiB
Markdown
154 lines
4.9 KiB
Markdown
---
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toc_priority: 47
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toc_title: Splitting and Merging Strings and Arrays
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---
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# Functions for Splitting and Merging Strings and Arrays {#functions-for-splitting-and-merging-strings-and-arrays}
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## splitByChar(separator, s) {#splitbycharseparator-s}
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Splits a string into substrings separated by a specified character. It uses a constant string `separator` which consisting 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>)
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```
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**Parameters**
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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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**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) of [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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``` 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(separator, s) {#splitbystringseparator-s}
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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>)
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```
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**Parameters**
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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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**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) of [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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``` 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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``` 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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## arrayStringConcat(arr\[, separator\]) {#arraystringconcatarr-separator}
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Concatenates the strings 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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## alphaTokens(s) {#alphatokenss}
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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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**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(text, regexp) {#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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**Parameters**
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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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Query:
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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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[Original article](https://clickhouse.tech/docs/en/query_language/functions/splitting_merging_functions/) <!--hide-->
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