Postgresql String Functions

#	Function	Return Type	Description
1	string concate	text	string concatenation
2	bit_length	int	Number of bits in string
3	char_length	int	Number of characters in string
4	character_length	int	Number of characters in string (The same as char_length())
5	lower	text	Convert string to lower case
6	octet_length	int	Number of bytes in string
7	overlay	text	Replace substring
8	position	int	Location of specified substring
9	substring	text	Extract substring and this function is also support the POSIX and SQL regular expression.
10	trim	text	Remove the longest string containing only the characters (a space by default) from the start/end/both ends of the string
11	upper	text	Convert string to upper case
12	ascii	int	ASCII code of the first character of the argument. For UTF8 returns the Unicode code point of the character. For other multibyte encodings, the argument must be an ASCII character
13	btrim	text	Remove the longest string consisting only of characters in characters (a space by default) from the start and end of string
14	chr	text	Character with the given code. For UTF8 the argument is treated as a Unicode code point. For other multibyte encodings the argument must designate an ASCII character. The NULL (0) character is not allowed because text data types cannot store such bytes.
15	concat	text	Concatenate all arguments. NULL arguments are ignored.
16	concat_ws	text	Concatenate all but first arguments with separators. The first parameter is used as a separator. NULL arguments are ignored.
17	convert	bytea	Convert string to dest_encoding. The original encoding is specified by src_encoding. The string must be valid in this encoding. Conversions can be defined by CREATE CONVERSION. Also there are some predefined conversions.
18	convert_from	text	Convert string to the database encoding. The original encoding is specified by src_encoding. The string must be valid in this encoding.
19	convert_to	bytea	Convert string to dest_encoding.
20	decode	bytea	Decode binary data from textual representation in string. Options for format are same as in encode.
21	encode	text	Encode binary data into a textual representation. Supported formats are: base64, hex, escape. escape merely outputs null bytes as \000 and doubles backslashes.
22	format	text	Format a string. This function is similar to the C function sprintf; but only the following conversion specifications are recognized: %s interpolates the corresponding argument as a string; %I escapes its argument as an SQL identifier; %L escapes its argument as an SQL literal; %% outputs a literal %. A conversion can reference an explicit parameter position by preceding the conversion specifier with n$, where n is the argument position.
23	initcap	text	Convert the first letter of each word to upper case and the rest to lower case. Words are sequences of alphanumeric characters separated by non-alphanumeric characters.
24	left	text	n| characters.
25	length	int	Number of characters in string
26	lpad	text	Fill up the string to length length by prepending the characters fill (a space by default). If the string is already longer than length then it is truncated (on the right).
27	ltrim	text	Remove the longest string containing only characters from characters (a space by default) from the start of string
28	md5	text	Calculates the MD5 hash of string, returning the result in hexadecimal
29	pg_client_encoding	name	Current client encoding name
30	quote_ident	text	Return the given string suitably quoted to be used as an identifier in an SQL statement string. Quotes are added only if necessary (i.e., if the string contains non-identifier characters or would be case-folded). Embedded quotes are properly doubled.
31	quote_literal	text	Return the given string suitably quoted to be used as a string literal in an SQL statement string. Embedded single-quotes and backslashes are properly doubled. Note that quote_literal returns null on null input; if the argument might be null, quote_nullable is often more suitable.
32	quote_literal	text	Coerce the given value to text and then quote it as a literal. Embedded single-quotes and backslashes are properly doubled.
33	quote_nullable	text	Return the given string suitably quoted to be used as a string literal in an SQL statement string; or, if the argument is null, return NULL. Embedded single-quotes and backslashes are properly doubled.
34	regexp_matches	setof text[]	Return all captured substrings resulting from matching a POSIX regular expression against the string.
35	regexp_replace	text	Replace substring(s) matching a POSIX regular expression. See Section 9.7.3 for more information.
36	regexp_split_to_array	text[]	Split string using a POSIX regular expression as the delimiter. See Section 9.7.3 for more information.
37	regexp_split_to_table	setof text	Split string using a POSIX regular expression as the delimiter. See Section 9.7.3 for more information.
38	repeat	text	Repeat string the specified number of times
39	replace	text	Replace all occurrences in string of substring from with substring to
40	reverse	text	Return reversed string.
41	right	text	n| characters.
42	rpad	text	Fill up the string to length length by appending the characters fill (a space by default). If the string is already longer than length then it is truncated.
43	rtrim	text	Remove the longest string containing only characters from characters (a space by default) from the end of string
44	split_part	text	Split string on delimiter and return the given field (counting from one)
45	strpos	int	Location of specified substring (same as position(substring in string), but note the reversed argument order)
46	substr	text	Extract substring (same as substring(string from from for count))
47	to_ascii	text	Convert string to ASCII from another encoding (only supports conversion from LATIN1, LATIN2, LATIN9, and WIN1250 encodings)
48	to_hex	text	Convert number to its equivalent hexadecimal representation
49	translate	text	Any character in string that matches a character in the from set is replaced by the corresponding character in the to set. If from is longer than to, occurrences of the extra characters in from are removed.