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Text Functions

This section describes functions and operators for examining and manipulating string values. The symbol denotes a space character.

Function Description Example Result Alias  
string ^@ search_string Alias for starts_with. 'abc' ^@ 'a' true starts_with  
string || string String concatenation 'Duck' || 'DB' DuckDB    
string[index] Alias for array_extract. 'DuckDB'[4] k array_extract  
string[begin:end] Alias for array_slice. Missing begin or end arguments are interpreted as the beginning or end of the list respectively. 'DuckDB'[:4] Duck array_slice  
string LIKE target Returns true if the string matches the like specifier (see Pattern Matching) 'hello' LIKE '%lo' true    
string SIMILAR TO regex Returns true if the string matches the regex; identical to regexp_full_match (see Pattern Matching) 'hello' SIMILAR TO 'l+' false    
array_extract(list, index) Extract a single character using a (1-based) index. array_extract('DuckDB', 2) u list_element, list_extract  
array_slice(list, begin, end) Extract a string using slice conventions. Negative values are accepted. array_slice('DuckDB', 5, NULL) DB    
ascii(string) Returns an integer that represents the Unicode code point of the first character of the string ascii('Ω') 937    
bar(x, min, max[, width]) Draw a band whose width is proportional to (x - min) and equal to width characters when x = max. width defaults to 80. bar(5, 0, 20, 10) ██▌    
bit_length(string) Number of bits in a string. bit_length('abc') 24    
chr(x) Returns a character which is corresponding the ASCII code value or Unicode code point chr(65) A    
concat_ws(separator, string, ...) Concatenate strings together separated by the specified separator concat_ws(', ', 'Banana', 'Apple', 'Melon') Banana, Apple, Melon    
concat(string, ...) Concatenate many strings together concat('Hello', ' ', 'World') Hello World    
contains(string, search_string) Return true if search_string is found within string contains('abc', 'a') true    
ends_with(string, search_string) Return true if string ends with search_string ends_with('abc', 'c') true suffix  
format_bytes(bytes) Converts bytes to a human-readable representation using units based on powers of 2 (KiB, MiB, GiB, etc.). format_bytes(16384) 16.0 KiB    
format(format, parameters...) Formats a string using the fmt syntax format('Benchmark "{}" took {} seconds', 'CSV', 42) Benchmark "CSV" took 42 seconds    
from_base64(string) Convert a base64 encoded string to a character string. from_base64('QQ==') 'A'    
hash(value) Returns a UBIGINT with the hash of the value hash('🦆') 2595805878642663834    
ilike_escape(string, like_specifier, escape_character) Returns true if the string matches the like_specifier (see Pattern Matching) using case-insensitive matching. escape_character is used to search for wildcard characters in the string. ilike_escape('A%c', 'a$%C', '$') true    
instr(string, search_string) Return location of first occurrence of search_string in string, counting from 1. Returns 0 if no match found. instr('test test', 'es') 2    
left_grapheme(string, count) Extract the left-most grapheme clusters left_grapheme('🤦🏼‍♂️🤦🏽‍♀️', 1) 🤦🏼‍♂️    
left(string, count) Extract the left-most count characters left('Hello🦆', 2) He    
length_grapheme(string) Number of grapheme clusters in string length_grapheme('🤦🏼‍♂️🤦🏽‍♀️') 2    
length(string) Number of characters in string length('Hello🦆') 6    
like_escape(string, like_specifier, escape_character) Returns true if the string matches the like_specifier (see Pattern Matching) using case-sensitive matching. escape_character is used to search for wildcard characters in the string. like_escape('a%c', 'a$%c', '$') true    
lower(string) Convert string to lower case lower('Hello') hello lcase  
lpad(string, count, character) Pads the string with the character from the left until it has count characters lpad('hello', 10, '>') >>>>>hello    
ltrim(string, characters) Removes any occurrences of any of the characters from the left sduide of the string ltrim('>>>>test<<', '><') test<<    
ltrim(string) Removes any spaces from the left side of the string ltrim('␣␣␣␣test␣␣') test␣␣    
md5(value) Returns the MD5 hash of the value md5('123') 202c...    
nfc_normalize(string) Convert string to Unicode NFC normalized string. Useful for comparisons and ordering if text data is mixed between NFC normalized and not. nfc_normalize('ardèch') ardèch    
not_ilike_escape(string, like_specifier, escape_character) Returns false if the string matches the like_specifier (see Pattern Matching) using case-sensitive matching. escape_character is used to search for wildcard characters in the string. not_ilike_escape('A%c', 'a$%C', '$') false    
not_like_escape(string, like_specifier, escape_character) Returns false if the string matches the like_specifier (see Pattern Matching) using case-insensitive matching. escape_character is used to search for wildcard characters in the string. not_like_escape('a%c', 'a$%c', '$') false    
ord(string) Return ASCII character code of the leftmost character in a string. ord('ü') 252    
parse_dirname(path, separator) Returns the top-level directory name from the given path. separator options: system, both_slash (default), forward_slash, backslash. parse_dirname('path/to/file.csv', 'system') path    
parse_dirpath(path, separator) Returns the head of the path (the pathname until the last slash) similarly to Python’s os.path.dirname function. separator options: system, both_slash (default), forward_slash, backslash. parse_dirpath('/path/to/file.csv', 'forward_slash') /path/to    
parse_filename(path, trim_extension, separator) Returns the last component of the path similarly to Python’s os.path.basename function. If trim_extension is true, the file extension will be removed (defaults to false). separator options: system, both_slash (default), forward_slash, backslash. parse_filename('path/to/file.csv', true, 'system') file    
parse_path(path, separator) Returns a list of the components (directories and filename) in the path similarly to Python’s pathlib.parts function. separator options: system, both_slash (default), forward_slash, backslash. parse_path('/path/to/file.csv', 'system') [/, path, to, file.csv]    
position(search_string in string) Return location of first occurrence of search_string in string, counting from 1. Returns 0 if no match found. position('b' in 'abc') 2    
printf(format, parameters...) Formats a string using printf syntax printf('Benchmark "%s" took %d seconds', 'CSV', 42) Benchmark "CSV" took 42 seconds    
read_text(source) Returns the content from source (a filename, a list of filenames, or a glob pattern) as a VARCHAR. The file content is first validated to be valid UTF-8. If read_text attempts to read a file with invalid UTF-8 an error is thrown suggesting to use read_blob instead. See the read_text guide for more details. read_text('hello.txt') hello\n    
regexp_escape(string) Escapes special patterns to turn string into a regular expression similarly to Python’s re.escape function regexp_escape('https://duckdb.org') https\:\/\/duckdb\.org    
regexp_extract_all(string, regex[, group = 0]) Split the string along the regex and extract all occurrences of group regexp_extract_all('hello_world', '([a-z ]+)_?', 1) [hello, world]    
regexp_extract(string, pattern , name_list); If string contains the regexp pattern, returns the capturing groups as a struct with corresponding names from name_list (see Pattern Matching) regexp_extract('2023-04-15', '(\d+)-(\d+)-(\d+)', ['y', 'm', 'd']) {'y':'2023', 'm':'04', 'd':'15'}    
regexp_extract(string, pattern [, idx]); If string contains the regexp pattern, returns the capturing group specified by optional parameter idx (see Pattern Matching) regexp_extract('hello_world', '([a-z ]+)_?', 1) hello    
regexp_full_match(string, regex) Returns true if the entire string matches the regex (see Pattern Matching) regexp_full_match('anabanana', '(an)*') false    
regexp_matches(string, pattern) Returns true if string contains the regexp pattern, false otherwise (see Pattern Matching) regexp_matches('anabanana', '(an)*') true    
regexp_replace(string, pattern, replacement); If string contains the regexp pattern, replaces the matching part with replacement (see Pattern Matching) regexp_replace('hello', '[lo]', '-') he-lo    
regexp_split_to_array(string, regex) Splits the string along the regex regexp_split_to_array('hello␣world; 42', ';?␣') ['hello', 'world', '42'] string_split_regex, str_split_regex  
regexp_split_to_table(string, regex) Splits the string along the regex and returns a row for each part regexp_split_to_array('hello␣world; 42', ';?␣') Two rows: 'hello', 'world'    
repeat(string, count) Repeats the string count number of times repeat('A', 5) AAAAA    
replace(string, source, target) Replaces any occurrences of the source with target in string replace('hello', 'l', '-') he--o    
reverse(string) Reverses the string reverse('hello') olleh    
right_grapheme(string, count) Extract the right-most count grapheme clusters right_grapheme('🤦🏼‍♂️🤦🏽‍♀️', 1) 🤦🏽‍♀️    
right(string, count) Extract the right-most count characters right('Hello🦆', 3) lo🦆    
rpad(string, count, character) Pads the string with the character from the right until it has count characters rpad('hello', 10, '<') hello<<<<<    
rtrim(string, characters) Removes any occurrences of any of the characters from the right side of the string rtrim('>>>>test<<', '><') >>>>test    
rtrim(string) Removes any spaces from the right side of the string rtrim('␣␣␣␣test␣␣') ␣␣␣␣test    
sha256(value) Returns a VARCHAR with the SHA-256 hash of the value sha-256('🦆') d7a5...    
split_part(string, separator, index) Split the string along the separator and return the data at the (1-based) index of the list. If the index is outside the bounds of the list, return an empty string (to match PostgreSQL’s behavior). split_part('a|b|c', '|', 2) b    
starts_with(string, search_string) Return true if string begins with search_string starts_with('abc', 'a') true    
str_split_regex(string, regex) Splits the string along the regex str_split_regex('hello␣world; 42', ';?␣') ['hello', 'world', '42'] string_split_regex, regexp_split_to_array  
string_split_regex(string, regex) Splits the string along the regex string_split_regex('hello␣world; 42', ';?␣') ['hello', 'world', '42'] str_split_regex, regexp_split_to_array  
string_split(string, separator) Splits the string along the separator string_split('hello␣world', '␣') ['hello', 'world'] str_split, string_to_array  
strip_accents(string) Strips accents from string strip_accents('mühleisen') muhleisen    
strlen(string) Number of bytes in string strlen('🦆') 4    
strpos(string, search_string) Alias for instr. Return location of first occurrence of search_string in string, counting from 1. Returns 0 if no match found. strpos('test test', 'es') 2 instr  
substring(string, start, length) Extract substring of length characters starting from character start. Note that a start value of 1 refers to the first character of the string. substring('Hello', 2, 2) el substr  
substring_grapheme(string, start, length) Extract substring of length grapheme clusters starting from character start. Note that a start value of 1 refers to the first character of the string. substring_grapheme('🦆🤦🏼‍♂️🤦🏽‍♀️🦆', 3, 2) 🤦🏽‍♀️🦆    
to_base64(blob) Convert a blob to a base64 encoded string. to_base64('A'::blob) QQ== base64  
trim(string, characters) Removes any occurrences of any of the characters from either side of the string trim('>>>>test<<', '><') test    
trim(string) Removes any spaces from either side of the string trim('␣␣␣␣test␣␣') test    
unicode(string) Returns the unicode code of the first character of the string unicode('ü') 252    
upper(string) Convert string to upper case upper('Hello') HELLO ucase  

Text Similarity Functions

These functions are used to measure the similarity of two strings using various similarity measures.

Function Description Example Result
damerau_levenshtein(s1, s2) Extension of Levenshtein distance to also include transposition of adjacent characters as an allowed edit operation. In other words, the minimum number of edit operations (insertions, deletions, substitutions or transpositions) required to change one string to another. Different case is considered different. damerau_levenshtein('duckdb', 'udckbd') 2
editdist3(s1, s2) Alias of levenshtein for SQLite compatibility. The minimum number of single-character edits (insertions, deletions or substitutions) required to change one string to the other. Different case is considered different. editdist3('duck', 'db') 3
jaccard(s1, s2) The Jaccard similarity between two strings. Different case is considered different. Returns a number between 0 and 1. jaccard('duck', 'luck') 0.6
jaro_similarity(s1, s2) The Jaro similarity between two strings. Different case is considered different. Returns a number between 0 and 1. jaro_similarity('duck', 'duckdb') 0.88
jaro_winkler_similarity(s1, s2) The Jaro-Winkler similarity between two strings. Different case is considered different. Returns a number between 0 and 1. jaro_winkler_similarity('duck', 'duckdb') 0.93
levenshtein(s1, s2) The minimum number of single-character edits (insertions, deletions or substitutions) required to change one string to the other. Different case is considered different. levenshtein('duck', 'db') 3
mismatches(s1, s2) Alias for hamming(s1, s2). The number of positions with different characters for two strings of equal length. Different case is considered different. mismatches('duck', 'luck') 1

Formatters

fmt Syntax

The format(format, parameters...) function formats strings, loosely following the syntax of the {fmt} open-source formatting library.

-- Format without additional parameters
SELECT format('Hello world'); -- Hello world
-- Format a string using {}
SELECT format('The answer is {}', 42); -- The answer is 42
// s == "The answer is 42."
-- Format a string using positional arguments
SELECT format('I''d rather be {1} than {0}.', 'right', 'happy'); -- I'd rather be happy than right.

Format Specifiers

Specifier Description Example
{:d} integer 123456
{:E} scientific notation 3.141593E+00
{:f} float 4.560000
{:o} octal 361100
{:s} string asd
{:x} hexadecimal 1e240
{:tX} integer, X is the thousand separator 123 456

Formatting Types

-- Integers
SELECT format('{} + {} = {}', 3, 5, 3 + 5); -- 3 + 5 = 8
-- Booleans
SELECT format('{} != {}', true, false); -- true != false
-- Format datetime values
SELECT format('{}', DATE '1992-01-01'); -- 1992-01-01
SELECT format('{}', TIME '12:01:00'); -- 12:01:00
SELECT format('{}', TIMESTAMP '1992-01-01 12:01:00'); -- 1992-01-01 12:01:00
-- Format BLOB
SELECT format('{}', BLOB '\x00hello'); -- \x00hello
-- Pad integers with 0s
SELECT format('{:04d}', 33); -- 0033
-- Create timestamps from integers
SELECT format('{:02d}:{:02d}:{:02d} {}', 12, 3, 16, 'AM'); -- 12:03:16 AM
-- Convert to hexadecimal
SELECT format('{:x}', 123_456_789); -- 75bcd15
-- Convert to binary
SELECT format('{:b}', 123_456_789); -- 111010110111100110100010101
SELECT format('{:,}',  123_456_789); -- 123,456,789
SELECT format('{:t.}', 123_456_789); -- 123.456.789
SELECT format('{:''}', 123_456_789); -- 123'456'789
SELECT format('{:_}',  123_456_789); -- 123_456_789
SELECT format('{:t }', 123_456_789); -- 123 456 789
SELECT format('{:tX}', 123_456_789); -- 123X456X789

printf Syntax

The printf(format, parameters...) function formats strings using the printf syntax.

-- Format without additional parameters
SELECT printf('Hello world');
-- output: Hello world
-- Format a string using arguments in a given order
SELECT printf('The answer to %s is %d', 'life', 42);
-- output: The answer to life is 42
-- Format a string using positional arguments '%position$formatter',
-- e.g., the second parameter as a string is encoded as '%2$s'
SELECT printf('I''d rather be %2$s than %1$s.', 'right', 'happy');
-- output: I'd rather be happy than right.

Format Specifiers

Specifier Description Example
%c character code to character a
%d integer 123456
%Xd integer with thousand seperarator X from ,, ., '', _ 123_456
%E scientific notation 3.141593E+00
%f float 4.560000
%hd integer 123456
%hhd integer 123456
%lld integer 123456
%o octal 361100
%s string asd
%x hexadecimal 1e240

Formatting Types

-- Integers
SELECT printf('%d + %d = %d', 3, 5, 3 + 5); -- 3 + 5 = 8
-- Booleans
SELECT printf('%s != %s', true, false); -- true != false
-- Format datetime values
SELECT printf('%s', DATE '1992-01-01'); -- 1992-01-01
SELECT printf('%s', TIME '12:01:00'); -- 12:01:00
SELECT printf('%s', TIMESTAMP '1992-01-01 12:01:00'); -- 1992-01-01 12:01:00
-- Format BLOB
SELECT printf('%s', BLOB '\x00hello'); -- \x00hello
-- Pad integers with 0s
SELECT printf('%04d', 33); -- 0033
-- Create timestamps from integers
SELECT printf('%02d:%02d:%02d %s', 12, 3, 16, 'AM'); -- 12:03:16 AM
-- Convert to hexadecimal
SELECT printf('%x', 123_456_789); -- 75bcd15
-- Convert to binary
SELECT printf('%b', 123_456_789); -- 111010110111100110100010101

Thousand Separators

SELECT printf('%,d',  123_456_789); -- 123,456,789
SELECT printf('%.d',  123_456_789); -- 123.456.789
SELECT printf('%''d', 123_456_789); -- 123'456'789
SELECT printf('%_d',  123_456_789); -- 123_456_789
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Last modified: 2024-03-02