SQL Reference

Qualified Column Names

A qualifier for a column name may be a table, view, nickname, alias, or correlation name.

Whether a column name may be qualified depends on its context:

• Depending on the form of the COMMENT ON statement, a single column name may need to be qualified. Multiple column names must be unqualified.
• Where the column name specifies values of the column, it may be qualified at the user's option.
• In all other contexts, a column name must not be qualified.

Where a qualifier is optional, it can serve two purposes. They are described under Column Name Qualifiers to Avoid Ambiguity and Column Name Qualifiers in Correlated References.