Qualified column names
A qualifier for a column name can be a table name, a view name, an alias name, or a correlation name.
Whether a column name can be qualified depends on its context:
- In the COMMENT and LABEL statements, the column name must be qualified.
- Where the column name specifies values of the column, a column name can be qualified.
- In the assignment-clause of an UPDATE statement, it may be qualified.
- In the column-name-list of an INSERT statement, it may be qualified.
- In all other contexts, a column name must not be qualified.
Where a qualifier is optional it can serve two purposes. See Column name qualifiers to avoid ambiguity and Column name qualifiers in correlated references for details.