String functions and operators

String operators

The || operator performs concatenation.

The LIKE statement can be used for pattern matching and is documented in like_operator{.interpreted-text role=“ref”}.

String functions

chr()

chr(n) → varchar
Returns the Unicode code point n as a single character string.

codepoint()

codepoint(string) → integer
Returns the Unicode code point of the only character of string.

concat()

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

concat_ws()

concat_ws(string0, string1, ..., stringN) → varchar
Returns the concatenation of string1, string2, ..., stringN using string0 as a separator. If string0 is null, then the return value is null. Any null values provided in the arguments after the separator are skipped.

concat_ws()

concat_ws(string0, array(varchar)) → varchar
Returns the concatenation of elements in the array using string0 as a separator. If string0 is null, then the return value is null. Any null values in the array are skipped.

format()

format(format, args...) → varchar
See format.

hamming_distance()

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()

length(string) → bigint
Returns the length of string in characters.

levenshtein_distance()

levenshtein_distance(string1, string2) → bigint
Returns the Levenshtein edit distance of string1 and string2, i.e. the minimum number of single-character edits (insertions, deletions or substitutions) needed to change string1 into string2.

lower()

lower(string) → varchar
Converts string to lowercase.

lpad()

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()

ltrim(string) → varchar
Removes leading whitespace from string.

luhn_check()

luhn_check(string) → boolean
Tests whether a string of digits is valid according to the Luhn algorithm. This checksum function, also known as modulo 10 or mod 10, is widely applied on credit card numbers and government identification numbers to distinguish valid numbers from mistyped, incorrect numbers.

Valid identification number:

select luhn_check(‘79927398713’); — true

Invalid identification number:

select luhn_check(‘79927398714’); — false

position()

position(substring IN string) → bigint

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

Note: This SQL-standard function has special syntax and uses the IN keyword for the arguments. See also strpos.

replace()

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.

reverse()

reverse(string) → varchar

Returns string with the characters

rpad()

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()

rtrim(string) → varchar

Removes trailing whitespace from string.

soundex()

soundex(char) → string

soundex returns a character string containing the phonetic representation of char.

It is typically used to evaluate the similarity of two expressions phonetically, that is how the string sounds when spoken:

    SELECT name
    FROM nation
    WHERE SOUNDEX(name)  = SOUNDEX('CHYNA');

     name  |
    -------+----
     CHINA |
    (1 row)

split()

split(string, delimiter) → array(varchar)

Splits string on delimiter and returns an array.

split()

split(string, delimiter, limit) → array(varchar)

Splits string on delimiter and returns an array of size at most limit. The last element in the array always contain everything left in the string. limit must be a positive number.

split_part()

split_part(string, delimiter, index) → varchar

Splits string on delimiter and returns the field index. Field indexes start with 1. If the index is larger than the number of fields, then null is returned.

split_to_map()

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.

split_to_multimap()

split_to_multimap(string, entryDelimiter, keyValueDelimiter) → map(varchar, array(varchar))

Splits string by entryDelimiter and keyValueDelimiter and returns a map containing an array of values for each unique key. entryDelimiter splits string into key-value pairs. keyValueDelimiter splits each pair into key and value. The values for each key will be in the same order as they appeared in string.

strpos()

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. When instance is a negative number the search will start from the end of string. Positions start with 1. If not found, 0 is returned.

starts_with()

starts_with(string, substring) → boolean

Tests whether substring is a prefix of string.

substring()

substr(string, start) → varchar

This is an alias for substring.

substring(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.

substr(string, start, length) → varchar

This is an alias for substring.

substring(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.

translate()

translate(source, from, to) → varchar

Returns the source string translated by replacing characters found in the

translate(source, from, to) → varchar

Returns the source string translated by replacing characters found in the from string with the corresponding characters in the to string. If the from string contains duplicates, only the first is used. If the source character does not exist in the from string, the source character will be copied without translation. If the index of the matching character in the from string is beyond the length of the to string, the source character will be omitted from the resulting string.

Here are some examples illustrating the translate function:

    SELECT translate('abcd', '', ''); -- 'abcd'
    SELECT translate('abcd', 'a', 'z'); -- 'zbcd'
    SELECT translate('abcda', 'a', 'z'); -- 'zbcdz'
    SELECT translate('Palhoça', 'ç','c'); -- 'Palhoca'
    SELECT translate('abcd', 'b', U&'\+01F600'); -- a😀cd
    SELECT translate('abcd', 'a', ''); -- 'bcd'
    SELECT translate('abcd', 'a', 'zy'); -- 'zbcd'
    SELECT translate('abcd', 'ac', 'z'); -- 'zbd'
    SELECT translate('abcd', 'aac', 'zq'); -- 'zbd'

trim()

trim(string) → varchar

Removes leading and trailing whitespace from string.

trim( \[ \[ specification \] \[ string \] FROM \] source ) → varchar

Removes any leading and/or trailing characters as specified up to and including string from source:

    SELECT trim('!' FROM '!foo!'); -- 'foo'
    SELECT trim(LEADING FROM '  abcd');  -- 'abcd'
    SELECT trim(BOTH '$' FROM '$var$'); -- 'var'
    SELECT trim(TRAILING 'ER' FROM upper('worker')); -- 'WORK'

upper()

upper(string) → varchar

Converts string to uppercase.

word_stem()

word_stem(word) → varchar

Returns the stem of word in the English language.

word_stem(word, lang) → varchar

Returns the stem of word in the lang language.

Unicode functions

normalize()

normalize(string) → varchar

Transforms string with NFC normalization form.

normalize(string, form) → varchar

Transforms string with the specified normalization form. form must be one of the following keywords:

Form	Description
NFD	Canonical Decomposition
NFC	Canonical Decomposition, followed by Canonical Composition
NFKD	Compatibility Decomposition
NFKC	Compatibility Decomposition, followed by Canonical Composition

to_utf8()

to_utf8(string) → varbinary

Encodes string into a UTF-8 varbinary representation.

from_utf8()

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.

from_utf8(binary, replace) → varchar

Decodes a UTF-8 encoded string from binary. Invalid UTF-8 sequences are replaced with replace. The replacement string replace must either be a single character or empty (in which case invalid characters are removed).