MySQL - String Functions

Compares sounds
Returns numeric value of left-most character
Returns a string representation of the argument
Returns length of argument in bits
Returns number of characters in argument
Returns the character for each integer passed
A synonym for CHAR_LENGTH()
Returns concatenate with  separator
Returns concatenated string
Converts numbers between different number bases
Returns string at index number
Returns a string such that for every bit set in the value  bits, you get an on string and for every unset bit, you get an off string
Returns the index (position) of the first argument  in the subsequent arguments
Returns the index position of  the first argument within the second argument
Returns a number formatted to specified number of decimal places
Returns a string representation of a hex value
Inserts a substring at the specified position up to  the specified number of characters
Returns the index of the first occurrence of substring
Synonym for LOWER()
Returns the leftmost number of characters as specified
Returns the length of a string in bytes
Loads the named file
Returns the position of the first occurrence  of substring
Returns the argument in lowercase
Returns the string argument, left-padded with the specified string
Removes leading spaces
Returns a set of comma-separated strings that have the corresponding bit in bits set
Returns a substring starting from the specified position
Returns a string representation of the octal argument
A synonym for LENGTH()
If the leftmost character of the  argument is a multi-byte character,  returns the code for that character
A synonym for LOCATE()
Escapes the argument for use in an SQL statement
Pattern matching using regular expressions
Repeats a string the specified number of times
Replaces occurrences of a specified string
Reverses the characters in a string
Returns the specified rightmost number of characters
Appends string the specified number of times
Removes trailing spaces
Returns a soundex string
Returns a string of the specified number of spaces
Compares two strings
Returns a substring from a  string before the specified number of occurrences of the delimiter
Returns the substring as specified
Removes leading and trailing spaces
Synonym for UPPER()
Converts each pair of hexadecimal digits to a character
Converts to uppercase
Returns the numeric value of the leftmost character of the string str. Returns 0 if str is the empty string. Returns NULL if str is NULL. ASCII() works for characters with numeric values from 0 to 255.
mysql> SELECT ASCII('2');
+---------------------------------------------------------+
|                       ASCII('2')                        |
+---------------------------------------------------------+
|                           50                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT ASCII('dx');
+---------------------------------------------------------+
|                       ASCII('dx')                       |
+---------------------------------------------------------+
|                          100                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns a string representation of the binary value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,2). Returns NULL if N is NULL.
mysql> SELECT BIN(12);
+---------------------------------------------------------+
|                          BIN(12)                        |
+---------------------------------------------------------+
|                           1100                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the length of the string str in bits.
mysql> SELECT BIT_LENGTH('text');
+---------------------------------------------------------+
|                   BIT_LENGTH('text')                    |
+---------------------------------------------------------+
|                          32                             |
+---------------------------------------------------------+
1 row in set (0.00 sec)
CHAR() interprets each argument N as an integer and returns a string consisting of the characters given by the code values of those integers. NULL values are skipped.
mysql> SELECT CHAR(77,121,83,81,'76');
+---------------------------------------------------------+
|                 CHAR(77,121,83,81,'76')                 |
+---------------------------------------------------------+
|                          MySQL                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the length of the string str, measured in characters. A multi-byte character counts as a single character. This means that for a string containing five two-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.
mysql> SELECT CHAR_LENGTH("text");
+---------------------------------------------------------+
|                   CHAR_LENGTH("text")                   |
+---------------------------------------------------------+
|                            4                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
CHARACTER_LENGTH() is a synonym for CHAR_LENGTH().
Returns the string that results from concatenating the arguments. May have one or more arguments. If all arguments are non-binary strings, the result is a non-binary string. If the arguments include any binary strings, the result is a binary string. A numeric argument is converted to its equivalent binary string form; if you want to avoid that, you can use an explicit type cast, as in this example: 
mysql> SELECT CONCAT('My', 'S', 'QL');
+---------------------------------------------------------+
|                 CONCAT('My', 'S', 'QL')                 |
+---------------------------------------------------------+
|                          MySQL                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
CONCAT_WS() stands for Concatenate With Separator and is a special form of CONCAT(). The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL.
mysql> SELECT CONCAT_WS(',','First name','Last Name' );
+---------------------------------------------------------+
|        CONCAT_WS(',','First name','Last Name' )         |
+---------------------------------------------------------+
|                 First name, Last Name                   |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Converts numbers between different number bases. Returns a string representation of the number N, converted from base from_base to base to_base. Returns NULL if any argument is NULL. The argument N is interpreted as an integer, but may be specified as an integer or a string. The minimum base is 2 and the maximum base is 36. If to_base is a negative number, N is regarded as a signed number. Otherwise, N is treated as unsigned. CONV() works with 64-bit precision.
mysql> SELECT CONV('a',16,2);
+---------------------------------------------------------+
|                     CONV('a',16,2)                      |
+---------------------------------------------------------+
|                          1010                           |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns str1 if N = 1, str2 if N = 2, and so on. Returns NULL if N is less than 1 or greater than the number of arguments. ELT() is the complement of FIELD().
mysql> SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo');
+---------------------------------------------------------+
|            ELT(1, 'ej', 'Heja', 'hej', 'foo')           |
+---------------------------------------------------------+
|                            ej                           |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns a string such that for every bit set in the value bits, you get an on string and for every bit not set in the value, you get an off string. Bits in bits are examined from right to left (from low-order to high-order bits). Strings are added to the result from left to right, separated by the separator string (the default being the comma character .,.). The number of bits examined is given by number_of_bits (defaults to 64).
mysql> SELECT EXPORT_SET(5,'Y','N',',',4);
+---------------------------------------------------------+
|              EXPORT_SET(5,'Y','N',',',4)                |
+---------------------------------------------------------+
|                        Y,N,Y,N                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the index (position starting with 1) of str in the str1, str2, str3, ... list. Returns 0 if str is not found.
mysql> SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo');
+---------------------------------------------------------+
|     FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo')      |
+---------------------------------------------------------+
|                           2                             |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns a value in the range of 1 to N if the string str is in the string list strlist consisting of N substrings.
mysql> SELECT FIND_IN_SET('b','a,b,c,d');
+---------------------------------------------------------+
|             SELECT FIND_IN_SET('b','a,b,c,d')           |
+---------------------------------------------------------+
|                            2                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Formats the number X to a format like '#,###,###.##', rounded to D decimal places, and returns the result as a string. If D is 0, the result has no decimal point or fractional part.
mysql> SELECT FORMAT(12332.123456, 4);
+---------------------------------------------------------+
|                FORMAT(12332.123456, 4)                  |
+---------------------------------------------------------+
|                     12,332.1235                         |
+---------------------------------------------------------+
1 row in set (0.00 sec)
If N_or_S is a number, returns a string representation of the hexadecimal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,16).
If N_or_S is a string, returns a hexadecimal string representation of N_or_S where each character in N_or_S is converted to two hexadecimal digits.
mysql> SELECT HEX(255);
+---------------------------------------------------------+
|                        HEX(255)                         |
+---------------------------------------------------------+
|                           FF                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT 0x616263;
+---------------------------------------------------------+
|                        0x616263                         |
+---------------------------------------------------------+
|                          abc                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str, with the substring beginning at position pos and len characters long replaced by the string newstr. Returns the original string if pos is not within the length of the string. Replaces the rest of the string from position pos if len is not within the length of the rest of the string. Returns NULL if any argument is NULL.
mysql> SELECT INSERT('Quadratic', 3, 4, 'What');
+---------------------------------------------------------+
|           INSERT('Quadratic', 3, 4, 'What')             |
+---------------------------------------------------------+
|                       QuWhattic                         |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the position of the first occurrence of substring substr in string str. This is the same as the two-argument form of LOCATE(), except that the order of the arguments is reversed.
mysql> SELECT INSTR('foobarbar', 'bar');
+---------------------------------------------------------+
|              INSTR('foobarbar', 'bar')                  |
+---------------------------------------------------------+
|                          4                              |
+---------------------------------------------------------+
1 row in set (0.00 sec)
LCASE() is a synonym for LOWER().
LEFT(str,len)
Returns the leftmost len characters from the string str, or NULL if any argument is NULL.
mysql> SELECT LEFT('foobarbar', 5);
+---------------------------------------------------------+
|                  LEFT('foobarbar', 5)                   |
+---------------------------------------------------------+
|                         fooba                           |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the length of the string str, measured in bytes. A multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.
mysql> SELECT LENGTH('text');
+---------------------------------------------------------+
|                      LENGTH('text')                     |
+---------------------------------------------------------+
|                            4                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Reads the file and returns the file contents as a string. To use this function, the file must be located on the server host, you must specify the full pathname to the file, and you must have the FILE privilege. The file must be readable by all and its size less than max_allowed_packet bytes.
If the file does not exist or cannot be read because one of the preceding conditions is not satisfied, the function returns NULL.
As of MySQL 5.0.19, the character_set_filesystem system variable controls interpretation of filenames that are given as literal strings.
mysql> UPDATE table_test
   -> SET blob_col = LOAD_FILE('/tmp/picture')
   -> WHERE id = 1;
...........................................................
The first syntax returns the position of the first occurrence of substring substr in string str. The second syntax returns the position of the first occurrence of substring substr in string str, starting at position pos. Returns 0 if substr is not in str.
mysql> SELECT LOCATE('bar', 'foobarbar');
+---------------------------------------------------------+
|                LOCATE('bar', 'foobarbar')               |
+---------------------------------------------------------+
|                            4                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str with all characters changed to lowercase according to the current character set mapping.
mysql> SELECT LOWER('QUADRATICALLY');
+---------------------------------------------------------+
|                 LOWER('QUADRATICALLY')                  |
+---------------------------------------------------------+
|                     quadratically                       |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str, left-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters.
mysql> SELECT LPAD('hi',4,'??');
+---------------------------------------------------------+
|                    LPAD('hi',4,'??')                    |
+---------------------------------------------------------+
|                          ??hi                           |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str with leading space characters removed.
mysql> SELECT LTRIM('  barbar');
+---------------------------------------------------------+
|                   LTRIM('  barbar')                     |
+---------------------------------------------------------+
|                        barbar                           |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns a set value (a string containing substrings separated by .,. characters) consisting of the strings that have the corresponding bit in bits set. str1 corresponds to bit 0, str2 to bit 1, and so on. NULL values in str1, str2, ... are not appended to the result.
mysql> SELECT MAKE_SET(1,'a','b','c');
+---------------------------------------------------------+
|                  MAKE_SET(1,'a','b','c')                |
+---------------------------------------------------------+
|                             a                           |
+---------------------------------------------------------+
1 row in set (0.00 sec)
MID(str,pos,len) is a synonym for SUBSTRING(str,pos,len).
Returns a string representation of the octal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,8). Returns NULL if N is NULL.
mysql> SELECT OCT(12);
+---------------------------------------------------------+
|                        OCT(12)                          |
+---------------------------------------------------------+
|                          14                             |
+---------------------------------------------------------+
1 row in set (0.00 sec)
OCTET_LENGTH() is a synonym for LENGTH().
If the leftmost character of the string str is a multi-byte character, returns the code for that character, calculated from the numeric values of its constituent bytes using this formula −
  (1st byte code)
+ (2nd byte code � 256)
+ (3rd byte code � 2562) ...
If the leftmost character is not a multi-byte character, ORD() returns the same value as the ASCII() function.
mysql> SELECT ORD('2');
+---------------------------------------------------------+
|                        ORD('2')                         |
+---------------------------------------------------------+
|                           50                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
POSITION(substr IN str) is a synonym for LOCATE(substr,str). 
Quotes a string to produce a result that can be used as a properly escaped data value in an SQL statement. The string is returned enclosed by single quotes and with each instance of single quote (','), backslash ('\'), ASCII NUL, and Control-Z preceded by a backslash. If the argument is NULL, the return value is the word 'NULL' without enclosing single quotes.
mysql> SELECT QUOTE('Don\'t!');
+---------------------------------------------------------+
|                     QUOTE('Don\'t!')                    |
+---------------------------------------------------------+
|                        'Don\'t!'                        |
+---------------------------------------------------------+
1 row in set (0.00 sec)
NOTE − Please check if your installation has any bug with this function, then don't use this function.
This function performs a pattern match of expr against pattern. Returns 1 if expr matches pat; otherwise it returns 0. If either expr or pat is NULL, the result is NULL. REGEXP is not case sensitive, except when used with binary strings.
mysql> SELECT 'ABCDEF' REGEXP 'A%C%%';
+---------------------------------------------------------+
|               'ABCDEF' REGEXP 'A%C%%'                   |
+---------------------------------------------------------+
|                         0                               |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Another example is −
mysql> SELECT 'ABCDE' REGEXP '.*';
+---------------------------------------------------------+
|                  'ABCDE' REGEXP '.*'                    |
+---------------------------------------------------------+
|                            1                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Let's see one more example −
mysql> SELECT 'new*\n*line' REGEXP 'new\\*.\\*line';
+---------------------------------------------------------+
|          'new*\n*line' REGEXP 'new\\*.\\*line'          |
+---------------------------------------------------------+
|                            1                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns a string consisting of the string str repeated count times. If count is less than 1, returns an empty string. Returns NULL if str or count are NULL.
mysql> SELECT REPEAT('MySQL', 3);
+---------------------------------------------------------+
|                   REPEAT('MySQL', 3)                    |
+---------------------------------------------------------+
|                    MySQLMySQLMySQL                      |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str.
mysql> SELECT REPLACE('www.mysql.com', 'w', 'Ww');
+---------------------------------------------------------+
|           REPLACE('www.mysql.com', 'w', 'Ww')           |
+---------------------------------------------------------+
|                   WwWwWw.mysql.com                      |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str with the order of the characters reversed.
mysql> SELECT REVERSE('abcd');
+---------------------------------------------------------+
|                      REVERSE('abcd')                    |
+---------------------------------------------------------+
|                           dcba                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the rightmost len characters from the string str, or NULL if any argument is NULL. 
mysql> SELECT RIGHT('foobarbar', 4);
+---------------------------------------------------------+
|                RIGHT('foobarbar', 4)                    |
+---------------------------------------------------------+
|                        rbar                             |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str, right-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters.
mysql> SELECT RPAD('hi',5,'?');
+---------------------------------------------------------+
|                     RPAD('hi',5,'?')                    |
+---------------------------------------------------------+
|                          hi???                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str with trailing space characters removed.
mysql> SELECT RTRIM('barbar   ');
+---------------------------------------------------------+
|                     RTRIM('barbar   ')                  |
+---------------------------------------------------------+
|                           barbar                        |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns a soundex string from str. Two strings that sound almost the same should have identical soundex strings. A standard soundex string is four characters long, but the SOUNDEX() function returns an arbitrarily long string. You can use SUBSTRING() on the result to get a standard soundex string. All non-alphabetic characters in str are ignored. All international alphabetic characters outside the A-Z range are treated as vowels.
mysql> SELECT SOUNDEX('Hello');
+---------------------------------------------------------+
|                   SOUNDEX('Hello')                      |
+---------------------------------------------------------+
|                         H400                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
This is the same as SOUNDEX(expr1) = SOUNDEX(expr2).
mysql> SELECT SPACE(6);
+---------------------------------------------------------+
|                     SELECT SPACE(6)                     |
+---------------------------------------------------------+
|                        '      '                         |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Compares two strings and returns 0 if both strings are equal, it returns -1 if the first argument is smaller than the second according to the current sort order otherwise it returns 1.
mysql> SELECT STRCMP('MOHD', 'MOHD');
+---------------------------------------------------------+
|                 STRCMP('MOHD', 'MOHD')                  |
+---------------------------------------------------------+
|                            0                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Another example is −
mysql> SELECT STRCMP('AMOHD', 'MOHD');
+---------------------------------------------------------+
|                STRCMP('AMOHD', 'MOHD')                                 |
+---------------------------------------------------------+
|                          -1                                                      |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Let's see one more example −
mysql> SELECT STRCMP('MOHD', 'AMOHD');
+---------------------------------------------------------+
|                STRCMP('MOHD', 'AMOHD')                                 |
+---------------------------------------------------------+
|                           1                                                       |
+---------------------------------------------------------+
1 row in set (0.00 sec)
The forms without a len argument return a substring from string str starting at position pos. The forms with a len argument return a substring len characters long from string str, starting at position pos. The forms that use FROM are standard SQL syntax. It is also possible to use a negative value for pos. In this case, the beginning of the substring is pos characters from the end of the string, rather than the beginning. A negative value may be used for pos in any of the forms of this function.
mysql> SELECT SUBSTRING('Quadratically',5);
+---------------------------------------------------------+
|              SSUBSTRING('Quadratically',5)              |
+---------------------------------------------------------+
|                       ratically                         |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT SUBSTRING('foobarbar' FROM 4);
+---------------------------------------------------------+
|              SUBSTRING('foobarbar' FROM 4)              |
+---------------------------------------------------------+
|                       barbar                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT SUBSTRING('Quadratically',5,6);
+---------------------------------------------------------+
|              SUBSTRING('Quadratically',5,6)             |
+---------------------------------------------------------+
|                         ratica                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim.
mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', 2);
+---------------------------------------------------------+
|         SUBSTRING_INDEX('www.mysql.com', '.', 2)        |
+---------------------------------------------------------+
|                         www.mysql                       |
+---------------------------------------------------------+
1 row in set (0.00 sec)
Returns the string str with all remstr prefixes or suffixes removed. If none of the specifiers BOTH, LEADING, or TRAILING is given, BOTH is assumed. remstr is optional and, if not specified, spaces are removed.
mysql> SELECT TRIM('  bar   ');
+---------------------------------------------------------+
|                     TRIM('  bar   ')                    |
+---------------------------------------------------------+
|                          bar                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
+---------------------------------------------------------+
|            TRIM(LEADING 'x' FROM 'xxxbarxxx')           |
+---------------------------------------------------------+
|                         barxxx                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
+---------------------------------------------------------+
|            TRIM(BOTH 'x' FROM 'xxxbarxxx')              |
+---------------------------------------------------------+
|                          bar                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
+---------------------------------------------------------+
|           TRIM(TRAILING 'xyz' FROM 'barxxyz')           |
+---------------------------------------------------------+
|                         barx                            |
+---------------------------------------------------------+
1 row in set (0.00 sec)
UCASE() is a synonym for UPPER().
Performs the inverse operation of HEX(str). That is, it interprets each pair of hexadecimal digits in the argument as a number and converts it to the character represented by the number. The resulting characters are returned as a binary string.
mysql> SELECT UNHEX('4D7953514C');
+---------------------------------------------------------+
|                    UNHEX('4D7953514C')                  |
+---------------------------------------------------------+
|                          MySQL                          |
+---------------------------------------------------------+
1 row in set (0.00 sec)
The characters in the argument string must be legal hexadecimal digits: '0' .. '9', 'A' .. 'F', 'a' .. 'f'. If UNHEX() encounters any non-hexadecimal digits in the argument, it returns NULL.
Returns the string str with all characters changed to uppercase according to the current character set mapping.
mysql> SELECT UPPER('Allah-hus-samad');
+---------------------------------------------------------+
|                  UPPER('Allah-hus-samad')               |
+---------------------------------------------------------+
|                      ALLAH-HUS-SAMAD                    |
+---------------------------------------------------------+
1 row in set (0.00 sec)
For more information, check MySQL Official Website - String Functions

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