[INFO] Autoincrement

[Ivan Smahin]

Hello Ruslan,

Saturday, May 7, 2005, 5:05:22 PM, you wrote:

RZ> On 5/7/05 4:45 PM, "Ivan Smahin"
RZ> <IvanSmahin at public.kherson.ua> wrote:

>> Hello All,
>> 
>>   Some database have such feature as autoincremental fields.
>>   Oracle has sequences. This object can be used just for getting
>>   unique value for a number purposes (including storing this value in
>>   any field).
>> 
>>   Common features of autoincremental fields:
>> 
>>   1. It can be INTEGER field only.
>>   2. Usually it is denied to write value to such field directly, but
>>      many DBMS allow this on your own risk (global DB parameter)
>>   3. Table may have only single autoincremental field. This is not
>>     strict requirement but it is no sense to have more.
>>   4. Usually only uniqueness is guaranteed. It can be gaps due to the
>>     delete operations. Some DB trying to reuse such gaps, but most of
>>     them just increase max value.
>>   5. If there is overflow - error generated.
>> 
>>   THE HUGE COMMON PROBLEM:
>> 
>>   Assume we have some dump - never mind in which format - xml or
>>   another. AutoIncremental field values also presented here as usual
>>   fields values.
>> 
>>   If we plan to continue using IDENTITY field we must notice LoadDump
>>   algorithm about this field. Its values must be recalculated very
>>   similar to the ObjectPtr values. ( Found all "ptrs" which use this
>>   autoincremental field and correct their values.

RZ> And this task is described by all: mySQL, Oracle, SQL Lite ?
RZ> They all can resolve this task of import ?

As a rule there is no automation. Just some tips and tricks for proper
load such dump. The same is true for replication purpose.



-- 
Best regards,
 Ivan                            mailto:IvanSmahin at public.kherson.ua

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