Beginning Oracle Database 11g Administration From Novice to Professional

26
CHAPTER 2 SQL AND PL/SQL
Data Definition Language
A large portion of the Oracle 11g SQL reference manual is devoted to DDL: commands
that are used to create, alter, and drop different types of database objects such as tables
and indexes.
Listing 2-4 shows the DDL commands that can be used to create the , ,
and tables used in the first chapter. These commands specify a data type such as
variable character () or numeric for each data item, the length of each data item,
and, in the case of numeric data items, the precision. indicates no more than
32 data characters, and indicates a decimal number with no more than eight
digits, two of which are to the right of the decimal point. Each of the three tables has a
primary key, and the table is linked to the other two tables by foreign keys. All data
items in this example are specified to be , which simply means that their values
cannot be left unspecified. Finally, note that each SQL statement is followed by a terminating
semicolon.
Listing 2-4. DDL Commands to Create the Supplier, Part, and Quote Tables
Database Manipulation Language
You have already seen several examples of the statement. Next, let’s consider the
, , , and statements.