Query cost: Global Temporary Tables vs. Collections (Virtual Arrays)

Question

I have a query whose results are stored in a GTT (Global Temporary Table) and in a Collection.

Selecting the data from the GTT again, I get a very small cost: 103.

Answer 1

The most important difference between collections and GTT in SQL, is that CBO(cost-based optimizer) has limitations for TABLE function (kokbf$...), for example JPPD doesn't work with TABLE() functions. Some workarounds: http://orasql.org/2019/05/30/workarounds-for-jppd-with-view-and-tablekokbf-xmltable-or-json_table-functions/