Why there is no primary key for tables

[ModyBuchbinder]

In Sql Server when I create a layer the OBJECTID is defined as primary key.

When I create a table (using ArcMap) the OBJECTID is not define as primary key.

See the screen shot, AAA is a layer (have a shape filed), BBB is a table.

Any reason for this?

Thanks

Mody

[shan_sarkar]

Mody,

Is BBB table is a non-spatial table?

~Shan

[ModyBuchbinder]

Yes I just did right click on the database connection and select  New->Table

[Asrujit_SenGupta]

There is a Unique Key created in case of Tables:

 

[ModyBuchbinder]

Index is not the same as primary key

See the key icon next to the OBJECTID field that exists in TESTFC and does not exists in TESTTABLE

[Asrujit_SenGupta]

What is an ObjectID?—Help | ArcGIS Desktop 

An ObjectID is a unique, not null integer field used to uniquely identify rows in tables in a geodatabase. ObjectIDs are limited to 32-bit values, which store a maximum value of 2,147,483,647.

So this satisfies the requirement for an ObjectID atleast.

Yes, they may not be the same and hence the question could be "Why does ArcGIS create a Primary Key in case of Feature Classes, but a Unique Index in case of Geodatabase Tables?"

[Asrujit_SenGupta]

From a quick test, it seems the behaviour is not same in an Oracle Enterprise gdb.

A Feature Class created in an Oracle sde gdb, does not have the ObjectID as a Primary Key. 

[FredSpataro]

I just ran into this issue... oddly it appears to be different if the database is 'geodatabase enabled' or not ... at least on SQL Server.  I just created a table via ArcCatalog on a plain/non-geodatabase database connection and the OBJECTID column is set as the primary key by default.