v$sql the details -- if you have multiple copies of the query:

"select * from T" in your shared pool, v$sql will have a row per query.

This can happen if user U1 and user U2 both have a table T and both issue "select * from T".

Those are entirely different queries with different plans and so on.

v$sql will have 2 rows.

v$sqlarea is a aggregate of v$sql. It selects out DISTINCT sql. "select * from T" will appear there.

It is not clear to me how you are joing v$session to v$sql to get more then one row.

If you wish to see the queries a session has open (maybe open, we cache
cursors so you might see some queries that are closed) use v$open_cursor by sid.

v$sqltext is simply a way to see the entire query. the v$sql and v$sqlarea
views only show the first 1000 bytes. newlines and other control characters are replace with whitespace.

v$sqltext_with_newlines is v$sqltext without the whitespace replacment.

V$SQL

V$SQL lists statistics on shared SQL area without the GROUP BY clause and contains one row for each child of the original SQL text entered.

V$SQLAREA

V$SQLAREA lists statistics on shared SQL area and contains one row per SQL string. It provides statistics on SQL statements that are in memory, parsed, and ready for execution.

V$SQLTEXT

This view contains the text of SQL statements belonging to shared SQL cursors in the SGA.

V$SQL_PLAN

V$SQL_PLAN contains the execution plan information for each child cursor loaded in the library cache.

V$SQLTEXT_WITH_NEWLINES

This view is identical to the V$SQLTEXT view except that, to improve legibility, V$SQLTEXT_WITH_NEWLINES does not replace newlines and tabs in the SQL statement with spaces.