As mentioned earlier, column names must be unique within each table. However, the same column name can be used in other tables. To uniquely identify names that are the same in multiple tables, we use a qualifying name.A qualified name is a table name followed by a period and the name of the column in the table.

                       Format:                         table_name.column_name

Tables must have unique names within a database. Therefore, a qualified name is unique within the database.

These two statements are functionally identical:

                    SELECT VNDR_ID,                          SELECT VENDOR_TBL.VNDR_ID
                                 VENDOR_NAME                              VENDOR_TBL.VENDOR_NAME
                       FROM VENDOR_TBL;                      FROM VENDOR_TBL;

> A column name does not need to be qualified if it is a unique name among all the column names of all the tables
used in a statement.> Qualified and unqualified names may be intermixed in a statement.

> It is a good idea to use qualified names. Then, if a matching name is added to another table in the future,
there will not be a problem with an unqualified name.

> Some RDBMS systems might require a hierarchy of qualification such as server, database, schema, owner, table.

> SQL Server requires server.database.owner.table.