SQL has three main commands for data definition: CREATE, for creating tables and databases; ALTER, for changing tables and databases; and DROP, for deleting tables and databases. Because creating, altering, and deleting databases are database administration tasks, we will consider only tables in this section.
We used the CREATE TABLE command in the previous chapter when we started building our sample database. The most basic form of this command is:
CREATE TABLE table_name ( column_1_name column_1_type, column_2_name column_2_type, column_n_name column_n_type );
which can have as few as one or as many as 1,000 columns. Although it is perfectly legal to omit a primary key in Oracle, it's a good practice ...