You name columns in CREATE TABLE and ALTER TABLE statements. In
    other SQL statements, the names you give to columns in CREATE and
    ALTER statements can be qualified by table names, view names, or
    correlation names.

                                   NOTE

       In syntax diagrams, the column-name syntax element refers to
       either the qualified or unqualified form of the name given
       to the column in the CREATE TABLE or ALTER TABLE statement.
       That is, in syntax diagrams, column-name is always defined
       as:

  column-name =

  ---+----------->-----------------+-> <name-of-column> -->
     +-> <table-name> -------+> . -+
     +-> <view-name> --------+
     +-> <correlation-name> -+

    The only time you must qualify column names is when they are
    ambiguous. Joining a table with itself and joining two tables
    with common column names are two cases that require qualified
    column names. Also, if you have a parameter without a colon with
    the same name as a column, you need to qualify references to that
    column.