How to create a deterministic uniqueidentifier (GUID) from an integer value - sql

Question

Note: This is not about database design nor about the general use of a GUID. This is about deterministically create such GUID's for test data, on a Microsoft SQL server.
We are migrating our database away from integer identifiers to the uniqueidentifier data type.
For test purposes we want to migrate our test data sets to known GUID values, deterministically based on our former integer values
UPDATE Unit
SET UnitGuid = NEWID(UnitId)
Obviously this does not work right away. How to use the UnitId to create a deterministic GUID?

Answer 1

You could create keymap table:
CREATE TABLE tab_map(id_old INT PRIMARY KEY, guid UNIQUEIDENTIFIER);
INSERT INTO tab_map(id_old, guid)
SELECT id, NEWID()
FROM src_table;
DBFiddle Demo
After that you could use simple query or wrap with a function:
SELECT guid
FROM tab_map
WHERE id_old = ?

Answer 2

Stop thinking about the problem from a "string" perspective. an int is made up of 4 bytes. A uniqueidentifier is made up of 16 bytes. you can easily take 12 fixed bytes and append the four bytes from an int to the end of those, and get a solution that works for all int values:
declare #Unit table
(
UniqueColumn UNIQUEIDENTIFIER DEFAULT NEWID(),
Characters VARCHAR(10),
IntegerId int
)
-- Add *3* data rows
INSERT INTO #Unit(Characters, IntegerId) VALUES ('abc', 1111),('def', 2222),('ghi',-17)
-- Deterministically creates a uniqueidentifier value out of an integer value.
DECLARE #GuidPrefix binary(12) = 0xefbeadde0000000000000000
UPDATE #Unit
SET UniqueColumn = CONVERT(uniqueidentifier,#GuidPrefix + CONVERT(binary(4),IntegerId))
-- Check the result
SELECT * FROM #Unit
Result:
UniqueColumn Characters IntegerId
------------------------------------ ---------- -----------
DEADBEEF-0000-0000-0000-000000000457 abc 1111
DEADBEEF-0000-0000-0000-0000000008AE def 2222
DEADBEEF-0000-0000-0000-0000FFFFFFEF ghi -17
(For various reasons, we have to provide the first four bytes in a different order than the one that is used by default when displaying a uniqueidentifier as a string, which is why if we want to display DEADBEEF, we had to start our binary as efbeadde)
Also, of course, insert usual warnings that if you're creating guids/uniqueidentifiers but not using one of the prescribed methods for generating them, then you cannot assume any of the usual guarantees about uniqueness.

Answer 3

I ended up solving this for myself. Here's my solution for future reference:
I create a prefix part of the GUID in the form of deadbeef-0000-0000-0000-, then append a "stringified", zero-padded version of the Id column's integer value to it, like 000000000001, wich results in
DEADBEEF-0000-0000-0000-000000000001
in this example.
Here's the SQL command for this action on a whole table:
-- Deterministically creates a uniqueidentifier value out of an integer value.
DECLARE #GuidPrefix nvarchar(max) = N'deadbeef-0000-0000-0000-'; -- without the last 12 digits
UPDATE Unit
SET UniqueColumn =
(SELECT #GuidPrefix + RIGHT('000000000000' + CAST(IntegerId AS NVARCHAR (12)), 12 ) AS NUMBER_CONVERTED)
Warnings:
This implementation works only for positive int values (which are up
to 2147483647 max)
This is only intended for test data! Use is
strongly discouraged for production data!
And here's a complete working example:
-- Create an example table with random GUID's
CREATE TABLE Unit
(
UniqueColumn UNIQUEIDENTIFIER DEFAULT NEWID(),
Characters VARCHAR(10),
IntegerId int
)
-- Add 2 data rows
INSERT INTO Unit(Characters, IntegerId) VALUES ('abc', 1111)
INSERT INTO Unit(Characters, IntegerId) VALUES ('def', 2222)
-- Deterministically creates a uniqueidentifier value out of an integer value.
DECLARE #GuidPrefix nvarchar(max) = N'deadbeef-0000-0000-0000-'; -- without the last 12 digits
UPDATE Unit
SET UniqueColumn =
(SELECT #GuidPrefix + RIGHT('000000000000' + CAST(IntegerId AS NVARCHAR (12)), 12 ) AS NUMBER_CONVERTED)
-- Check the result
SELECT * FROM Unit
Result:
UniqueColumn Characters IntegerId
--------------------------------------- ---------- ---------
DEADBEEF-0000-0000-0000-000000001111 abc 1111
DEADBEEF-0000-0000-0000-000000002222 def 2222