SQL String Functions

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SQL String Functions

Serial number	Name	Description	Note
1	ASCII ()	Returns the value of the leftmost character	ASCII code of the source content can be used in a pair of char () data parsing import operations;
2	CHAR ()	Returns the character of each passed integer
3	HEX ()	Returns the string representation of a hexadecimal value	Unhex () can be used for data import operation with Hex pairing;
4	Unhex ()	Converts each pair of hexadecimal digits to one character

ASCII (STR)

Returns the value of the leftmost character of the string str. If Str is an empty string, return 0. , then null STR is returned as NULL. The ASCII () character that applies to numeric values from 0 to 255.

sql> SELECT ASCII (' 2 ');

+---------------------------------------------------------+

| ASCII (' 2 ') |

+---------------------------------------------------------+

| 50 |

+---------------------------------------------------------+

1 row in Set (0.00 sec)

sql> SELECT ASCII (' DX ');

+---------------------------------------------------------+

| ASCII (' DX ') |

+---------------------------------------------------------+

| 100 |

+---------------------------------------------------------+

1 row in Set (0.00 sec)

CHAR () interprets each parameter n as an integer and returns a string of characters given by the code value of those integers. A null value was skipped.

Sql> SELECT CHAR (77,121,83,81, ' 76 ');

+---------------------------------------------------------+

| CHAR (77,121,83,81, ' 76 ') |

+---------------------------------------------------------+

| MySQL |

+---------------------------------------------------------+

1 row in Set (0.00 sec)

HEX (n_or_s)

If n_or_s is a number, returns N, where n is a string representation of the hexadecimal value of 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 n_or_s each character is converted to two hexadecimal digits.

sql> SELECT HEX (255);

+---------------------------------------------------------+

| HEX (255) |

+---------------------------------------------------------+

| FF |

+---------------------------------------------------------+

1 row in Set (0.00 sec)

Sql> SELECT 0x616263;

+---------------------------------------------------------+

| 0x616263 |

+---------------------------------------------------------+

| ABC |

+---------------------------------------------------------+

1 row in Set (0.00 sec)

Unhex (STR)

Executes the inverse of Hex (STR). That is, it interprets the arguments for each pair of hexadecimal digits as numbers and converts them to characters represented by numbers. The resulting character is returned as a binary string.

sql> SELECT unhex (' 4d7953514c ');

+---------------------------------------------------------+

| Unhex (' 4d7953514c ') |

+---------------------------------------------------------+

| SQL |

+---------------------------------------------------------+

1 row in Set (0.00 sec)

The character in the argument string must be a valid hexadecimal number: ' 0 ' ... ' 9 ', ' A ' ... ' F ', ' one ' ... F '. If Unhex () encounters any non-hexadecimal number in the parameter, it returns NULL.

SQL String Functions