为什么MySQL允许VARCHAR（255）拥有更大的数字

Question

When I first learnt about field types in MySQL I would define anything that was not a number as a VARCHAR and set the length to anything. 500 2000, but am I right in saying the maximum is actually 255?

If this is the case, why does MySQL let me define columns with much larger lengths and what is it actually doing? Will it allow larger lengths? Does it define the column / field as something else?

Any advice welcomed.

Answer 1

This behavior was changed after 5.0.3:

Values in VARCHAR columns are variable-length strings. The length can be specified as a value from 0 to 255 before MySQL 5.0.3, and 0 to 65,535 in 5.0.3 and later versions. The effective maximum length of a VARCHAR in MySQL 5.0.3 and later is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used.

From The CHAR and VARCHAR Types documentation reference.