Column references
A column reference cannot contain any spaces.
	Syntax
[[[database.]schema.]table-name.]column-name
Parameters
| schema | Database and schema. The default schema is public. If you specify a database, it must be the current database. | 
| table-name  | One of the following: 
 | 
| column-name  | A column name that is unique among all queried tables. | 
Restrictions
A column reference cannot contain any spaces.