sql - Why does VARCHAR need length specification?

Question

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

Why do we always need to specify VARCHAR(length) instead of just VARCHAR? It is dynamic anyway.

UPD: I'm puzzled specifically by the fact that it is mandatory (e.g. in MySQL).

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1 Answer

深蓝 · Answer 1 · 2021-10-16T23:59:32+0000

The "length" of the VARCHAR is not the length of the contents, it is the maximum length of the contents.

The max length of a VARCHAR is not dynamic, it is fixed and therefore has to be specified.

If you don't want to define a maximum size for it then use VARCHAR(MAX).