Which two statements are true regarding subqueries? (Choose two.)
A.
A subquery can retrieve zero or more rows.
B.
Only two subqueries can be placed at one level.
C.
A subquery can be used only in SQL query statements.
D.
A subquery can appear on either side of a comparison operator.
E.
There is no limit on the number of subquery levels in the WHERE clause of a SELECT statement.
Alguém sabe explicar o motivo da ‘E’ estar incorreta e a ‘D’ correta?
Oracle allows a maximum nesting of 255 subquery levels in a WHERE clause. There is no limit for nesting subqueries expressed in a FROM clause.In practice, the limit of 255 levels is not really a limit at all because it is rare to encounter subqueries nested beyond three or four levels.
Leandro,o Oracle não impôs limite de utilização de subquery na clausula FROM, no entanto o limite é de 255 na clausulá WHERE.
Conforme nota da Oracle na versão 10g,
http://docs.oracle.com/cd/B19306_01/server.102/b14200/queries007.htm
E mantida na versão 12c
https://docs.oracle.com/database/121/SQLRF/queries007.htm#SQLRF52357