My current understanding:

  • Oracle has index-organized tables and defaults to heap-organized.
  • I heard that SQL-Server uses only index-organized tables

I'm especially thinking about solutions for MySQL, Informix and DB2.

SQL Server can store table data either in Heap Structures or Clustered Index Structures. If your table does not possess a clustered index then its considered a heap. For additional particulars see here Heap Structures and Clustered Index Structures

MySql has clustered indexes but there seems to become limited control on these indexes.

MySql clustered indexes and find out this here

DB2 has MDC (multi-dimension cluster) which could effectively index organise the table in a number of ways. I have not used at all them however, you can most likely simply have just one dimension MDC which will be the just like a typical clustered index.

Oracle is a little of the discomfort. Before I checked using its IOT implementation requires you produce the table as IOT and also you can't change it out later, that is annoying when you wish to load a lot of information without any indexes for speed after which index it after.

For Informix Dynamic Server (IDS) or Standard Engine (SE), both of them support clustered and non-clustered indexes. IDS uses RSAM and SE uses C-ISAM B-Tree indexing. For, whenever a cluster index is produced, a table's rows are physically purchased within the same order because the index, but as new rows are put into the table, the row is physically placed at EOF (heap).