ข้อส่งสัยเกี่ยวกับ varchar ผมส่งสัยมานานแล้วครับ เกี่ยวกับ varchar ใน Mysql คือว่า varcharมันจะเก็บค่า ตามที่เขตข้อมูลนั้นมีอยู่จริง

Quote:

[NATIONAL] VARCHAR(M) [CHARACTER SET charset_name] [COLLATE collation_name]

A variable-length string. M represents the maximum column length in characters. The range of M is 0 to 65,535. The effective maximum length of a VARCHAR is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used. For example, utf8 characters can require up to three bytes per character, so a VARCHAR column that uses the utf8 character set can be declared to be a maximum of 21,844 characters.

MySQL stores VARCHAR values as a one-byte or two-byte length prefix plus data. The length prefix indicates the number of bytes in the value. A VARCHAR column uses one length byte if values require no more than 255 bytes, two length bytes if values may require more than 255 bytes.