ClickHouse/docs/en/query_language/functions/splitting_merging_functions.md

Functions for splitting and merging strings and arrays

splitByChar

Splits a string into substrings separated by a specified character. It uses a constant string separator which consisting of exactly one character.

Syntax

splitByChar(<separator>, <s>)

Parameters

• separator — The separator which should contain exactly one character. String.
• s — The string to split. String.

Returned value(s)

Returns an array of selected substrings. Empty substrings may be selected when:

• A separator occurs at the beginning or end of the string;
• There are multiple consecutive separators;
• The original string s is empty.

Type: Array of String.

Example

SELECT splitByChar(',', '1,2,3,abcde')

┌─splitByChar(',', '1,2,3,abcde')─┐
│ ['1','2','3','abcde']           │
└─────────────────────────────────┘

splitByString

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.

Syntax

splitByString(<separator>, <s>)

Parameters

• separator — The separator. String.
• s — The string to split. String.

Returned value(s)

Returns an array of selected substrings. Empty substrings may be selected when:

• A non-empty separator occurs at the beginning or end of the string;
• There are multiple consecutive non-empty separators;
• The original string s is empty while the separator is not empty.

Type: Array of String.

Example

SELECT splitByString(', ', '1, 2 3, 4,5, abcde')

┌─splitByString(', ', '1, 2 3, 4,5, abcde')─┐
│ ['1','2 3','4,5','abcde']                 │
└───────────────────────────────────────────┘

SELECT splitByString('', 'abcde')

┌─splitByString('', 'abcde')─┐
│ ['a','b','c','d','e']      │
└────────────────────────────┘

arrayStringConcat(arr[, separator])

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. Returns the string.

alphaTokens(s)

Selects substrings of consecutive bytes from the ranges a-z and A-Z.Returns an array of substrings.

Example

SELECT alphaTokens('abca1abc')

┌─alphaTokens('abca1abc')─┐
│ ['abca','abc']          │
└─────────────────────────┘

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