If a column is not associated with an explicit table name, tables named in the SQL statement are searched, and one of the following occurs.
|IF this …||IS …||THEN …|
|a matching column||found in only one table||the requested information is returned.|
|found in two or more tables||an ambiguous column name error is reported.|
|not found||the NAMED list is searched for the column name.
Named names are not valid when used to fully qualify a table name.
|a column name||not found in the SQL statement or in the NAMED list||a nonexistent column error is reported.|