問題文
An employee table holds the identifier of each manager in one of its own columns and a report has to show each employee next to the name of the manager. Which approach fits?
選択肢
- The table is queried twice and the two results are combined with a set operator so that the rows of the managers follow the rows of the employees.
- The table is grouped by the identifier of the manager so that each group carries the name of the manager as well as the names of the members.
- The table is paired to itself without any alias so that the database works out which side plays the employee role from the column names.
- The table is joined to itself under two different aliases so that one alias plays the employee role and the other plays the manager role.