MySQL string functions (1) | MySQL string functions (2)

If the result length is greater than the server parameter max_allowed_packet, the string value function returns NULL. For operations on the string position, the first position is marked as 1. ASCII (str) returns the ASCII code value of the leftmost character of the str string. If str is a Null String, 0 is returned. If 'str' is NULL, return NULL. M

If the result length is greater than the server parameter max_allowed_packet, the string value function returns NULL. For operations on the string position, the first position is marked as 1. ASCII (str) returns the ASCII code value of the leftmost character of the str string. If str is a Null String, 0 is returned. If 'str' is NULL, return NULL. M

If the result length is greater than the server parametermax_allowed_packet, String value function returnNULL.

For operations on the string position, the first position is marked as 1.

ASCII(str)

Returns a string. strASCII code value of the leftmost character. If strIs a null string and returns 0. If strYes NULL, Return NULL.

mysql> select ASCII('2');        -> 50mysql> select ASCII(2);        -> 50mysql> select ASCII('dx');        -> 100

For more information, see the ORD () function.

ORD(str)

If the leftmost character of a string 'str' is a multi-byte character ((first byte ASCII code)*256+(second byte ASCII code))[*256+third byte ASCII code...]Returns the ASCII code value of a character to return the multi-byte code. If the leftmost character is not a multi-byte character. Returns and ASCII()The same value returned by the function.

mysql> select ORD('2');        -> 50 

CONV(N,from_base,to_base)

Convert numbers between different digit bases. Return number NString number, from from_baseBase transform to_baseBase, if any parameter is NULL, Return NULL. Parameters NIt is interpreted as an integer, but can be specified as an integer or a string. Minimum base is 2And the largest base is 36. If to_baseIs a negative number, NIt is considered as a signed number. Otherwise, NIt is treated as an unsigned number. CONVWork with 64-point precision.

mysql> select CONV("a",16,2);        -> '1010'mysql> select CONV("6E",18,8);        -> '172'mysql> select CONV(-17,10,-18);        -> '-H'mysql> select CONV(10+"10"+'10'+0xa,10,10);        -> '40' 

BIN(N)

Returns the binary value. NIn NIs a long integer ( BIGINT) Number, which is equivalent CONV(N,10,2). If NYes NULL, Return NULL.

mysql> select BIN(12);        -> '1100'

OCT(N)

Returns the octal value. NRepresents a string in NIs a long integer, which is equivalent CONV(N,10,8). If NIs NULL, return NULL.

mysql> select OCT(12);        -> '14' 

HEX(N)

Returns the hexadecimal value. NRepresents a string. NIs a long integer ( BIGINT) Number, which is equivalent CONV(N,10,16). If NYes NULL, Return NULL.

mysql> select HEX(255);        -> 'FF' 

CHAR(N,...)

CHAR()Interpreted as an integer and returns a string consisting of ASCII code characters of these integers. NULLThe value is skipped.

mysql> select CHAR(77,121,83,81,'76');        -> 'MySQL'mysql> select CHAR(77,77.3,'77.3');        -> 'MMM' 

CONCAT(str1,str2,...)

Returns a string from the parameter link. If any parameter is NULL, Return NULL. There can be more than two parameters. A numeric parameter is converted to an equivalent string.

mysql> select CONCAT('My', 'S', 'QL');        -> 'MySQL'mysql> select CONCAT('My', NULL, 'QL');        -> NULLmysql> select CONCAT(14.3);        -> '14.3'

LENGTH(str)

　

OCTET_LENGTH(str)

　

CHAR_LENGTH(str)

　

CHARACTER_LENGTH(str)

Returns a string. str.

mysql> select LENGTH('text');        -> 4mysql> select OCTET_LENGTH('text');        -> 4

Note that for multi-byte characters, its CHAR_LENGTH () is calculated only once.

LOCATE(substr,str)

　

POSITION(substr IN str)

Returns a substring. substrIn the string strThe first position that appears, if substrNot in strAnd returns 0.

mysql> select LOCATE('bar', 'foobarbar');        -> 4mysql> select LOCATE('xbar', 'foobar');        -> 0

This function is multi-byte reliable.

LOCATE(substr,str,pos)

Returns a substring. substrIn the string strThe first position that appears, starting from the position posStart. If substrNot in strAnd returns 0.

mysql> select LOCATE('bar', 'foobarbar',5);        -> 7

This function is multi-byte reliable.

INSTR(str,substr)

Returns a substring. substrIn the string strThe first position in. This is in the form of two parameters LOCATE()Same, except that the parameters are reversed.

mysql> select INSTR('foobarbar', 'bar');        -> 4mysql> select INSTR('xbar', 'foobar');        -> 0

This function is multi-byte reliable.

LPAD(str,len,padstr)

Returns a string. str, Use a string on the left padstrFill strYes lenCharacters long.

mysql> select LPAD('hi',4,'??');        -> '??hi' 

RPAD(str,len,padstr)

Returns a string. str, String on the right padstrFill strYes lenCharacters long.

mysql> select RPAD('hi',5,'?');        -> 'hi???'

LEFT(str,len)

Returns a string. strThe leftmost area lenCharacters.

mysql> select LEFT('foobarbar', 5);        -> 'fooba'

This function is multi-byte reliable.

RIGHT(str,len)

Returns a string. strThe rightmost lenCharacters 。

mysql> select RIGHT('foobarbar', 4);        -> 'rbar'

This function is multi-byte reliable.