How should I store a Guid in Oracle

Question

I am coming from the SQL server world where we had uniqueidentifier. Is there an equivalent in oracle? This column will be frequently queried so performance is the key.

I am generating the GUID in .Net and will be passing it to Oracle. For a couple reasons it cannot be generated by oracle so I cannot use sequence.

Answer 1

There is no uniqueidentifier in Oracle.

You can implement one yourself by using RAW (kind of a pain) or CHAR. Performance on queries that JOIN on a CHAR field will suffer (maybe as much as 40%) in comparison with using an integer.

If you're doing distributed/replicated databases, the performance hit is worth it. Otherwise, just use an integer.

Answer 2

The general practice using Oracle is to create an artificial key. This is a column defined as a number. It is populated via a sequence. It is indexed/constrained via a primary key definition.

Answer 3

CREATE table test (testguid RAW(16) default SYS_GUID() )

This blog studied the relative performance.

Answer 4

If I understand the question properly, you want to generate a unique id when you insert a row in the db.
You could use a sequence to do this. link here
Once you have created your sequence you can use it like this:

INSERT INTO mytable (col1, col2) VALUES (myseq.NEXTVAL, 'some other data');

Answer 5

GUIDs are not as used in Oracle as in MSSQL, we tend to have a NUMBER field (not null & primary key) , a sequence, and a trigger on insert to populate it (for every table).

Answer 6

As others have stated, there is a performance hit using GUIDs compared to numeric sequences. That said, there is a function named "SYS_GUID()" available since Oracle 8i that provides the raw equivalent:

SQL> SELECT SYS_GUID() FROM DUAL;

SYS_GUID()
--------------------------------
248AACE7F7DE424E8B9E1F31A9F101D5

A function could be created to return a formatted GUID:

CREATE OR REPLACE FUNCTION GET_FORMATTED_GUID RETURN VARCHAR2 IS guid VARCHAR2(38) ;
BEGIN
    SELECT SYS_GUID() INTO guid FROM DUAL ;

    guid :=
        '{' || SUBSTR(guid,  1, 8) ||
        '-' || SUBSTR(guid,  9, 4) ||
        '-' || SUBSTR(guid, 13, 4) ||
        '-' || SUBSTR(guid, 17, 4) ||
        '-' || SUBSTR(guid, 21) || '}' ;

    RETURN guid ;
END GET_FORMATTED_GUID ;
/

Thus returning an interchangeable string:

SQL> SELECT GET_FORMATTED_GUID() FROM DUAL ;

GET_FORMATTED_GUID()
--------------------------------------
{15417950-9197-4ADD-BD49-BA043F262180}

A note of caution should be made that some Oracle platforms return similar but still unique values of GUIDs as noted by Steven Feuerstein.