Relational Data - Functions - String Replace Functions

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General strings functions and functions for searching in strings are described separately.

overlay

Replace part of the string input with another string replace, starting at the 1-based index offset.

Syntax 

overlay(s, replace, offset[, length])

Parameters

  • input: A string type String.
  • replace: A string type String.
  • offset: An integer type Int. If offset is negative, it is counted from the end of the input string.
  • length: Optional. An integer type Int. length specifies the length of the snippet within input to be replaced. If length is not specified, the number of bytes removed from input equals the length of replace; otherwise length bytes are removed.

Returned value

Example 

SELECT overlay('ClickHouse SQL', 'CORE', 12) AS res;

Result: 

┌─res─────────────┐
│ ClickHouse CORE │
└─────────────────┘

overlayUTF8

Replace part of the string input with another string replace, starting at the 1-based index offset.

Assumes that the string contains valid UTF-8 encoded text. If this assumption is violated, no exception is thrown and the result is undefined.

Syntax 

overlayUTF8(s, replace, offset[, length])

Parameters

  • s: A string type String.
  • replace: A string type String.
  • offset: An integer type Int. If offset is negative, it is counted from the end of the input string.
  • length: Optional. An integer type Int. length specifies the length of the snippet within input to be replaced. If length is not specified, the number of characters removed from input equals the length of replace; otherwise length characters are removed.

Returned value

Example 

SELECT overlayUTF8('ClickHouse是一款OLAP数据库', '开源', 12, 2) AS res;

Result: 

┌─res────────────────────────┐
│ ClickHouse是开源OLAP数据库   │
└────────────────────────────┘

replaceOne

Replaces the first occurrence of the substring pattern in haystack by the replacement string.

Syntax 

replaceOne(haystack, pattern, replacement)

replaceAll

Replaces all occurrences of the substring pattern in haystack by the replacement string.

Syntax 

replaceAll(haystack, pattern, replacement)

Alias: replace.

replaceRegexpOne

Replaces the first occurrence of the substring matching the regular expression pattern (in re2 syntax) in haystack by the replacement string.

replacement can contain 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 

replaceRegexpOne(haystack, pattern, replacement)

Example

Converting ISO dates to American format: 

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: 

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: 

SELECT replaceRegexpOne('Hello, World!', '.*', '\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0') AS res

Result: 

┌─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 

SELECT replaceRegexpAll('Hello, World!', '.', '\\0\\0') AS res

Result: 

┌─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.: 

SELECT replaceRegexpAll('Hello, World!', '^', 'here: ') AS res

Result: 

┌─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

Syntax 

regexpQuoteMeta(s)

format

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: {{ 'Template:' and Template:'' }}. Field names can be numbers (starting from zero) or empty (then they are implicitly given monotonically increasing numbers).

Syntax 

format(pattern, s0, s1, ...)

Example 

SELECT format('{1} {0} {1}', 'World', 'Hello')
┌─format('{1} {0} {1}', 'World', 'Hello')─┐
│ Hello World Hello                       │
└─────────────────────────────────────────┘

With implicit numbers: 

SELECT format('{} {}', 'Hello', 'World')
┌─format('{} {}', 'Hello', 'World')─┐
│ Hello World                       │
└───────────────────────────────────┘

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 

translate(s, from, to)

Example 

SELECT translate('Hello, World!', 'delor', 'DELOR') AS res

Result: 

┌─res───────────┐
│ HELLO, WORLD! │
└───────────────┘

translateUTF8

Like translate but assumes s, from and to are UTF-8 encoded strings.

Syntax 

translateUTF8(s, from, to)

Parameters

Returned value

Examples

Query: 

SELECT translateUTF8('Münchener Straße', 'üß', 'us') AS res;
┌─res──────────────┐
│ Munchener Strase │
└──────────────────┘

printf

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 %%.

Syntax 

printf(format, arg1, arg2, ...)

Example

Query: 

select printf('%%%s %s %d', 'Hello', 'World', 2024);
┌─printf('%%%s %s %d', 'Hello', 'World', 2024)─┐
│ %Hello World 2024                            │
└──────────────────────────────────────────────┘
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