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This article mainly introduces which is the function of mysql to find the length. It is very detailed and has a certain reference value. Friends who are interested must read it!

The mysql function for length is the length () function and the char_length () function; where the length () function returns the length of a string in bytes, and the char_length () function returns the length of a string in characters.

Both char_length function and length function in MySQL can return the length of a string.

Mysql > select length ('MySQL'), char_length (' MySQL') +-+-+ | length ('MySQL') | char_length (' MySQL') | +-+-+ | 5 | +- -+-+ 1 row in set (0.01 sec)

The functions of the two functions:

LENGTH () returns the length of the string in bytes.

CHAR_LENGTH () returns the length of a string in characters.

Judging from the above example, "MySQL" has a total of 5 characters, and each character should occupy 1 byte.

While Chinese is different, generally a Chinese character accounts for 2-3 bytes. Such as:

Under the GBK character set encoding:

Select char_length ('China'); / / 2 characters select length ('China'); / / 4 bytes, a Chinese character 2 bytes select bit_length ('China'); / / 32 bits. 4: 8 = 32

Under the UTF8 character set encoding:

Select char_length ('China'); / / 2 characters select length ('China'); / / 6 bytes, a Chinese character 3 bytes select bit_length ('China'); / / 48 bits. 6 8 = 48

Summary

Char_length (str)

The unit of length is a character, and a multi-byte character counts as a single character.

Whether a Chinese character or a number or a letter is a character.

Length (str)

Under utf8 coding, a Chinese character is counted as three characters, and a number or letter as a character.

Under other codes, a Chinese character is counted as two characters, and a number or letter as a character.

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