问题
We are using UUID as primary key for out oracle DB, and trying to determine an appropriate max character length for the VARCHAR. Apparently this is 36 characters but we have noticed UUID'S generated which are longer than this - up to 60 characters in length. Does anyone know a suitable max char length for UUID??
回答1:
Section 3 of RFC4122 provides the formal definition of UUID string representations. It's 36 characters (32 hex digits + 4 dashes).
Sounds like you need to figure out where the invalid 60-char IDs are coming from and decide 1) if you want to accept them, and 2) what the max length of those IDs might be based on whatever API is used to generate them.
回答2:
This is the perfect kind of field to define as CHAR 36, by the way, not VARCHAR 36, since each value will have the exact same length. And you'll use less storage space, since you don't need to store the data length for each value, just the value.
回答3:
Most databases have a native UUID type these days to make working with them easier. If yours doesn't, they're just 128-bit numbers, so you can use BINARY(16), and if you need the text format frequently, e.g. for troubleshooting, then add a calculated column to generate it automatically from the binary column. There is no good reason to store the (much larger) text form.
来源：https://stackoverflow.com/questions/13397038/uuid-max-character-length