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*
To retrieve all columns from all tables and views
in the FROM list, enter a single asterisk ( * ) as the sole argument of the
select list clause.
name.*
When selecting columns from one or more tables or views, you can select all
columns from a particular table by qualifying the special asterisk character
with the appropriate name, which can be a table name, view name, or
correlation name, designating a table or view named in the FROM clause.
NULL
A derived column consisting entirely of null values can be specified using
the NULL keyword.
value expression
Typically, unless SELECT * is used (see above), one or more value expressions,
separated by commas, make up the select list portion of the statement.
These value expressions
can be column names, functions, character or numeric constants, or some arithmetic
combination of columns, functions, and constants. Expressions can be optionally
enclosed by parentheses and nested (with the exception of aggregate functions,
which may not be nested).
alias
A name for the output of the value expression or the NULL column.
If no alias is specified and the value expression is a direct column reference,
the name of the output column will be the column name referenced. If no alias
is specified and the value expression is not a direct column reference, the
name of the output column will be its position number in the output table,
counting from left to right.