Which of the following set operations in SQL automatically removes duplicate tuples from the final combined result by default?
UNION combines query results and eliminates duplicate rows by default. To preserve duplicate rows, UNION ALL must be used.
Which SQL set operation returns only the rows that are present in the first query result but NOT present in the second query result?
The EXCEPT operator (called MINUS in Oracle) performs set difference, returning distinct rows from the first query that do not appear in the second query.
What is a 'View' in SQL?
A View is a virtual relation containing no stored data tuples of its own; its definition (query) is stored in the data dictionary and executed dynamically when referenced.
Which SQL command is used to remove an existing View definition from the database?
Because views are schema objects, they are removed using the DDL command DROP VIEW.
Which of the following constraints in SQL can be defined at either the column level or the table level?
PRIMARY KEY, FOREIGN KEY, UNIQUE, and CHECK constraints can all be declared as either column-level constraints or table-level constraints.