Which one faster- With Rowid or PK

Question

Hi,
Recently came across the concepts of IOT(Index organised table). It was mentioned that
You must specify a primary key for an index-organized table, because the primary key uniquely identifies a row. Use the primary key instead of the Rowid for directly
accessing index-organized rows. "
This surprised me as till date I was assuming that the fastest way to access the data from a table is by Rowid. Isn't this contadicting then?
Can the experts clarify more on these conceps related to IOT.
Rgds,
Aashish

Answer 1

what is the diff betn a Normal table with PK on some column and IOT with almost
the same structure?The difference is whatever is implied by that "almost".
Look, the purpose of index organized tables is to do away with a nugatory object when a table and and its primary key index - have basically the same structure. The classic example is the code lookup table, where the difference between the table's columns (code, code_descr) and its primary key (code) is a single column (code_descr). Nearly access of that table is going to be an indexed read on code to get the description. That usage makes it a good candidate for being an IOT.
Mere creation of PK on a column would give the same result.No. An index organized table is similar to creating an index on (code, code_descr) but without the need to maintain two sets of data. Furthermore the IOT allows us to include non-primary key columns without compromising our relational integrity.
Cheers, APC
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