Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 2 SQL AND PL/SQL 47
in SQL.
diagrams can include subdiagrams and can even refer to themselves in recursive
fashion. For instance, a table reference can be an entire subquery—this kind of
subquery is called an inline view. The list can include scalar subquery expressions—subqueries
that return exactly one data item from exactly one data row.
and Data Definition
Language (DDL). DML includes the , , , , and statements.
DDL includes the , , and statements for the different classes
of objects in an Oracle database. The SQL reference manual also describes commands
that can be used to perform database administration activities such as
stopping and starting databases.
municate
with the database.
a prohibition against duplicates causes queries that are seemingly equivalent to
produce differing results and inhibits the query optimization process.
mizer
may not always choose the same query execution plan in all cases, even
though the query plan that is most efficient in one case is obviously the most efficient
for all other cases.
programs has many advantages, including efficiency, control, and flexibility. PL/SQL
offers a full complement of structured programming mechanisms such as condition
checking, loops, and subroutines.