Is there UID datatype in SQLITE if Yes then how to generate value for that

问题

I am creating table like this:

CREATE TABLE foobar (id uniqueidentifier, foo text, bar text, PRIMARY  KEY (id))

How to insert or generate value for id field in table foobar?

回答1:

You can argue that SQLite doesn't support data types at all. In SQLite3, you can do this, for example.

sqlite> create table test (id wibblewibble primary key);

SQLite will happily create a column with the "data type" wibblewibble. SQLite will also happily create columns with the "data types" uuid, guid, and SuperChicken.

The crucial point for you is probably how to automatically generate a uid. SQLite can't help you much there.

You can leave it entirely up to the client program. If you're programming in python, use the uuid module. In ruby, you have the SecureRandom.uuid function. Other languages have similar features or workarounds.

You can write your own uid-generating function in C. (See Create or Redefine SQL Functions.) I'd call this a relatively extreme approach.

You can store it in either binary or text format.

Other conversations online suggest that there's a widespread misunderstanding about what a UUID is. A UUID is not simply a 128-bit random number. A UUID has structure and rules. See RFC 4122.

回答2:

Benjamin Berry's answer isn't right — it produces malformed UUIDs — but it shows an interesting technique using a subselect to generate randomness then selecting substrings from that. Here's something similar that I've confirmed does work:

select substr(u,1,8)||'-'||substr(u,9,4)||'-4'||substr(u,13,3)||
  '-'||v||substr(u,17,3)||'-'||substr(u,21,12) from (
    select lower(hex(randomblob(16))) as u, substr('89ab',abs(random()) % 4 + 1, 1) as v);

Some sample output:

c71122df-18e4-4a78-a446-fbf7b8f2969b
61e75f87-978b-4d9e-b587-bedcc2d23898
30eee0fa-2ff2-4ff5-b8ef-f99378272999

回答3:

Here is something similar which can be used directly as a expression:

lower(hex(randomblob(4))) || '-' || lower(hex(randomblob(2))) || '-4' || substr(lower(hex(randomblob(2))),2) || '-' || substr('89ab',abs(random()) % 4 + 1, 1) || substr(lower(hex(randomblob(2))),2) || '-' || lower(hex(randomblob(6)))

for example to be passed as default value for column:

sqlite> create table "table" (
  "id" char(36) default (lower(hex(randomblob(4))) || '-' || lower(hex(randomblob(2))) || '-4' || substr(lower(hex(randomblob(2))),2) || '-' || substr('89ab',abs(random()) % 4 + 1, 1) || substr(lower(hex(randomblob(2))),2) || '-' || lower(hex(randomblob(6)))), 
  "data" varchar(255), primary key ("id")
);

sqlite> insert into "table" ("data") values ('foo');
sqlite> insert into "table" ("data") values ('bar');
sqlite> select * from "table";
947efcc9-4212-442a-b68c-eb6fbd8a7128|foo
a2c3857b-1eb4-40bd-aed2-6e8d68cc2ab8|bar

回答4:

needed this for a project

select SUBSTR(UUID, 0, 8)||'-'||SUBSTR(UUID,8,4)||'-'||SUBSTR(UUID,12,4)||'-'||SUBSTR(UUID,16)
from (
select lower(hex(randomblob(16))) AS UUID 
);

来源：https://stackoverflow.com/questions/10104662/is-there-uid-datatype-in-sqlite-if-yes-then-how-to-generate-value-for-that

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sqlite

uid