mysql字符串操作（MySQL string manipulation）.doc

mysql字符串操作（MySQL string manipulation） Note: if the length of the result is greater than the server parameter max_allowed_packet, the string value function returns NULL For action on string position, the first position is marked 1. ASCII (STR) Returns the ASCII code value of the leftmost character of string str. If STR is an empty string, return 0. If STR is NULL, return NULL. Mysql select ASCII (2); - 50 Mysql select ASCII (2); - 50 Mysql select ASCII (DX); - 100 Also see the ORD () function. ORD (STR) If the string STR, the leftmost character is a multi byte character, in second (first, byte, code, *256+, ASCII, code), [*256+third, byte, ASCII, code, byte, ASCII... Returns the ASCII code value of the character to return the multi byte character code. If the leftmost character is not a multi - byte character. Returns the same value returned by the ASCII () function. Mysql select ORD (2); - 50 More... CONV (N, from_base, to_base) Change numbers between different numbers of bases. Returns the string number of the numeric N, from the from_base base to the to_base base, and returns NULL if any parameter is NULL. The parameter N is interpreted as an integer, but can be specified as either an integer or a string. The smallest base is 2, and the largest base is 36. If to_base is a negative number, N is considered a signed number, otherwise N is treated as an unsigned number. CONV works at a precision of 64 loci. 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 a string representation of the binary value N, where N is a long integer (BIGINT) number, which is equivalent to CONV (N, 10,2). If N is NULL, return NULL. Mysql select BIN (12); 1100 - OCT (N) Returns the representation of a string of octal value N, where N is a long integer number, which is equivalent to CONV (N, 10,8). If N is NULL, return NULL. Mysql select OCT (12);