So i was reading MySQL innoDB, which apparently stores table data by default on a clustered Index (b+tree) based on primary key, and the tuples are in the leafs of that b+tree
https://blog.jcole.us/2013/01/10/btree-index-structures-in-innodb/
i was wondering do all the famous Relational DBMSes like PostgreSQL, Oracle, SQL server, SQLite, store it the same way? by making a clustered Index (b+tree) based on primary key and store data on the leafs of tree?
and does Clustered index on primary key in databases basically mean storing the table based on primary key on a B+tree table?
(sorry if this is a general question but i cant make 4-5 seperate questions asking the same for each of the databases i mentioned, if you only know about one or few of them please tell)
also if its a database does not use clustered by default, can you explain how does it structure the files, for example do they make a b+tree on primary key which the leafs point to some sort of address inside a heap or...?
EDIT :
so far we got the answers for all of them except SQLite, if anyone have any info on how tables are actually stored in SQLite by default please do tell.