Keywords are any reserved SQL terms which have a fixed, systematic meaning to the server. Some common examples of keywords are INSERT , UPDATE , SELECT , and DELETE .
All SQL commands are keywords, though many keywords themselves are not complete commands. For instance, the command INSERT INTO is a valid SQL command, and the word INTO is a reserved keyword. As you might guess, however, the word INTO has no particular significance when used out of context.
Identifiers, as described earlier, are variable names which reference database objects. These names are arbitrarily designated by the creator of the database object upon creation. The objects which can be referred to by identifiers in PostgreSQL may be databases, tables, columns, indices, views, sequences, rules, triggers or functions.
Example 3-2 adds three pieces of information about Oregon into a simple table called states .
Example 3-2. Keywords and Commands
booktown=# INSERT INTO states VALUES (33, 'Oregon', 'OR'); INSERT 3389701 1
In examining the statement in Example 3-2 , you will see the use of the SQL keywords INSERT , INTO , and VALUES , as illustrated via the INSERT INTO SQL command.
The table referenced by the states identifier is what is then modified by the INSERT INTO command. The modification in this case is the insertion of a new record.