String Functions

Note

These functions assume that the input strings contain valid UTF-8 encoded Unicode code points. There are no explicit checks for valid UTF-8 and the functions may return incorrect results on invalid UTF-8.

Additionally, the functions operate on Unicode code points and not user visible characters (or grapheme clusters). Some languages combine multiple code points into a single user-perceived character, the basic unit of a writing system for a language, but the functions will treat each code point as a separate unit.

The lower() and upper() functions do not perform locale-sensitive, context-sensitive, or one-to-many mappings required for some languages. Specifically, this will return incorrect results for Lithuanian, Turkish and Azeri.

chr(n) varchar

Returns the Unicode code point n as a single character string.

codepoint(string) integer

Returns the Unicode code point of the only character of string.

concat(string1, ..., stringN) varchar

Returns the concatenation of string1, string2, ..., stringN. This function provides the same functionality as the SQL-standard concatenation operator (||).

ends_with(string, substring) boolean

Returns whether string ends_with with substring.

from_utf8(binary) varchar

Decodes a UTF-8 encoded string from binary. Invalid UTF-8 sequences are replaced with the Unicode replacement character U+FFFD. Each invalid UTF-8 codepoint, including those of multi-byte long, is replaced with one replacement character.

from_utf8(binary, replace) varchar

Decodes a UTF-8 encoded string from binary. Invalid UTF-8 sequences are replaced with replace. Each invalid UTF-8 codepoint, including those of multi-byte long, is replaced with one replacement character. The replace argument can be either Unicode code point (bigint), a single character or empty string. When replace is an empty string invalid characters are removed.

hamming_distance(string1, string2) bigint

Returns the Hamming distance of string1 and string2, i.e. the number of positions at which the corresponding characters are different. Note that the two strings must have the same length.

length(string) bigint

Returns the length of string in characters.

levenshtein_distance(string_1, string_2) bigint

Returns the Levenshtein edit distance of 2 strings. I.e. the minimum number of single-character edits (insertions, deletions or substitutions) needed to convert string_1 to string_2.

lower(string) varchar

Converts string to lowercase.

lpad(string, size, padstring) varchar

Left pads string to size characters with padstring. If size is less than the length of string, the result is truncated to size characters. size must not be negative and padstring must be non-empty.

ltrim(string) varchar

Removes leading whitespace from string. See trim() for the set of recognized whitespace characters.

ltrim(string, chars) varchar

Removes the longest substring containing only characters in chars from the beginning of the string.

SELECT ltrim('test', 't'); -- est
SELECT ltrim('tetris', 'te'); -- ris
replace(string, search) varchar

Removes all instances of search from string.

replace(string, search, replace) varchar

Replaces all instances of search with replace in string.

If search is an empty string, inserts replace in front of every character and at the end of the string.

reverse(string) varchar

Returns input string with characters in reverse order.

reverse(varbinary) varbinary

Returns input binary with bytes in reversed order.

rpad(string, size, padstring) varchar

Right pads string to size characters with padstring. If size is less than the length of string, the result is truncated to size characters. size must not be negative and padstring must be non-empty.

rtrim(string) varchar

Removes trailing whitespace from string. See trim() for the set of recognized whitespace characters.

rtrim(string, chars) varchar

Removes the longest substring containing only characters in chars from the end of the string.

SELECT rtrim('test', 't'); -- tes
SELECT rtrim('test...', '.'); -- test
split(string, delimiter)

Splits string on delimiter and returns an array.

split(string, delimiter, limit)

Splits string on delimiter and returns an array of size at most limit.

The last element in the array always contains everything left in the string. limit must be a positive number.

split_part(string, delimiter, index) string

Splits string on delimiter and returns the part at index index.

Field indexes start with 1. If the index is larger than the number of fields, then null is returned.

split_to_map(string, entryDelimiter, keyValueDelimiter) map<varchar, varchar>

Splits string by entryDelimiter and keyValueDelimiter and returns a map. entryDelimiter splits string into key-value pairs. keyValueDelimiter splits each pair into key and value. Note that entryDelimiter and keyValueDelimiter are interpreted literally, i.e., as full string matches.

entryDelimiter and keyValueDelimiter must not be empty and must not be the same. entryDelimiter is allowed to be the trailing character.

Raises an error if there are duplicate keys.

starts_with(string, substring) boolean

Returns whether string starts with substring.

strpos(string, substring) bigint

Returns the starting position of the first instance of substring in string. Positions start with 1. If not found, 0 is returned.

strpos(string, substring, instance) bigint

Returns the position of the N-th instance of substring in string. instance must be a positive number. Positions start with 1. If not found, 0 is returned. It takes into account overlapping strings when counting occurrences.

SELECT strpos('aaa', 'aa', 2); -- 2
strrpos(string, substring) bigint

Returns the starting position of the last instance of substring in string. Positions start with 1. If not found, 0 is returned.

strrpos(string, substring, instance) bigint

Returns the position of the N-th instance of substring in string starting from the end of the string. instance must be a positive number. Positions start with 1. If not found, 0 is returned. It takes into account overlapping strings when counting occurrences.

SELECT strrpos('aaa', 'aa', 2); -- 1
substr(string, start) varchar

Returns the rest of string from the starting position start. Positions start with 1. A negative starting position is interpreted as being relative to the end of the string. Returns empty string if absolute value of start is greater then length of the string.

substr(string, start, length) varchar

Returns a substring from string of length length from the starting position start. Positions start with 1. A negative starting position is interpreted as being relative to the end of the string. Returns empty string if absolute value of 'start is greater then length of the string.

trim(string) varchar

Removes starting and ending whitespaces from string.

Recognized whitespace characters:

Code

Description

Code

Description

9

TAB (horizontal tab)

U+1680

Ogham Space Mark

10

LF (NL line feed, new line)

U+2000

En Quad

11

VT (vertical tab)

U+2001

Em Quad

12

FF (NP form feed, new page)

U+2002

En Space

13

CR (carriage return)

U+2003

Em Space

28

FS (file separator)

U+2004

Three-Per-Em Space

29

GS (group separator)

U+2005

Four-Per-Em Space

30

RS (record separator)

U+2006

Four-Per-Em Space

31

US (unit separator)

U+2008

Punctuation Space

32

Space

U+2009

Thin Space

_

_

U+200a

Hair Space

_

_

U+200a

Hair Space

_

_

U+2028

Line Separator

_

_

U+2029

Paragraph Separator

_

_

U+205f

Medium Mathematical Space

_

_

U+3000

Ideographic Space

trim(string, chars) varchar

Removes the longest substring containing only characters in chars from the beginning and end of the string.

SELECT trim('test', 't'); -- es
SELECT trim('.t.e.s.t.', '.t'); -- e.s
upper(string) varchar

Converts string to uppercase.

word_stem(word) varchar

Returns the stem of word in the English language. If the word is not an English word, the word in lowercase is returned.

word_stem(word, lang) varchar

Returns the stem of word in the lang language. This function supports the following languages:

lang

Language

ca

Catalan

da

Danish

de

German

en

English

es

Spanish

eu

Basque

fi

Finnish

fr

French

hu

Hungarian

hy

Armenian

ir

Irish

it

Italian

lt

Lithuanian

nl

Dutch

no

Norwegian

pt

Portuguese

ro

Romanian

ru

Russian

sv

Swedish

tr

Turkish

If the specified lang is not supported, this function throws a user error.

Unicode Functions

to_utf8(string) varbinary

Encodes string into a UTF-8 varbinary representation.