SQL Server dbo.sysdiagrams is a user table or system table

Question

When use Database Diagrams in a simple database, SQL Server create a dbo.sysdiagrams table in the Table\Systam Tables node (in Microsoft management studio\object explorer). But sysdiagrams table marked as user table in SQL Server. you can get user table by below query.

SELECT *  FROM sys.tables t WHERE OBJECTPROPERTY(t.object_id,'IsUserTable') = 1 

I don't know that sysdiagram table is a system table or is a user table.

Exists microsoft_database_tools_support with value 1 In the extended property of sysdiagram, that determine this table created automatically.

Answer 1

Management Studio utilizes the following in its determination of "System Objects" where "tbl" is sys.tables:

CAST(  case      when tbl.is_ms_shipped = 1 then 1     when (         select              major_id          from              sys.extended_properties          where              major_id = tbl.object_id and              minor_id = 0 and              class = 1 and              name = N'microsoft_database_tools_support')          is not null then 1     else 0 end                        AS bit) AS [IsSystemObject]