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How to Generate Version 1 UUIDs
Message
From
19/09/2017 10:10:16
Cetin Basoz
Engineerica Inc.
Izmir, Turkey
 
 
To
19/09/2017 04:18:52
General information
Forum:
Visual FoxPro
Category:
Client/server
Environment versions
Visual FoxPro:
VFP 9 SP2
OS:
Windows 7
Network:
SAMBA Server
Database:
MySQL
Application:
Desktop
Miscellaneous
Thread ID:
01654423
Message ID:
01654432
Views:
88
This message has been marked as the solution to the initial question of the thread.
>Hi Experts,
>
>For the longest time, I have been using CoCreateGuid and StringFromGUID2 to generate GUIDs. Problem with this is, whenever one simply does "select * from customer" from a MySQL Server, it does not show the customer rows in its sequential order of creation/insertion. I either need to add a column that is autoinc in nature to enforce sequential behavior.
>
>If one calls or invokes the UUID() of MySQL (or PHP), these GUID values can be spliced and reorganized to make the inserted rows sequential. This is possible due to the fact that the GUIDs they produced are of type "version 1", wherein the 4th and 5th segments are fixed. I won't be needing the added overhead of creating autoinc columns.
>
>This cannot be done however when one uses CoCreateGuid and StringFromGUID2 as the GUIDs they give are of type version 4 - wherein each segment is totally random.
>
>Aside from making a call to a MySQL server, "select uuid()" to populate my primary keys, is there another way to do this "natively"? Needless to say, this will save me a trip to the server.
>
>Thanks In Advance.

IMHO when the backend is not VFP, you shouldn't rely on insertion order and explicitly order by some column if you ever want the result ordered. Second, you shouldn't create clustered indexes for the primary key when the key is a GUID (I don't know if MySQL has it or if it has what it is called there-data is inserted in the order of the key and is default for primary keys unless otherwise specified).

Having said that, here is a code that use UuidCreateSequential instead:
*uniqueIDSequential.prg
Declare Integer CoCreateGuid In 'OLE32.dll' ;
  string @pguid
Declare Integer StringFromGUID2 In 'OLE32.dll' ;
  string rguid, String @lpsz, Integer cchMax
Declare Integer UuidCreateSequential In 'RPCRT4.dll'  String @ Uuid

Local pguid,rguid, lcOldError, lnResult
pguid=Replicate(Chr(0),16)
rguid=Replicate(Chr(0),80)
lcOldError = On('error')
On Error lnResult = CoCreateGuid(@pguid)
lnResult = UuidCreateSequential(@pguid)
On Error &lcOldError
Return ;
  Iif( InList(m.lnResult,0,1824) And ;
  StringFromGUID2(pguid,@rguid,40) # 0, ;
  StrConv(Left(rguid,76),10), "" )
Çetin Basöz

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