SQL Identifiers

SQL identifiers are used to identify objects in the database, such as table names, view
names, and columns. The characters that can be used in a user-defined SQL identifier must
appear in a character set. The ISO standard provides a default character set, which consists
of the upper-case letters A . . . Z, the lower-case letters a . . . z, the digits 0 . . . 9, and
the underscore (_) character. It is also possible to specify an alternative character set. The
following restrictions are imposed on an identifier:
n an identifier can be no longer than 128 characters (most dialects have a much lower
limit than this);
n an identifier must start with a letter;
n an identifier cannot contain spaces.
Data type Declarations
boolean BOOLEAN
character CHAR VARCHAR
bit† BIT BIT VARYING
exact numeric NUMERIC DECIMAL INTEGER SMALLINT
approximate numeric FLOAT REAL DOUBLE PRECISION
datetime DATE TIME TIMESTAMP
interval INTERVAL
large objects CHARACTER LARGE OBJECT BINARY LARGE OBJECT