Informatics Practices
What is the correct statement for describing the UNION operation ?
- It combines the rows of any two different queries
- It combines the unique rows of two different queries which have the same set of attributes in the select clause
- It combines the rows of two different queries which have the same condition in the where clause
- It gives the Cartesian product of the results of any two queries
Answer
It combines the unique rows of two different queries which have the same set of attributes in the select clause
Reason — The UNION operation in SQL combines the results of two queries into a single result set, including only distinct rows from both queries. The queries must have the same number of columns having similar data types and order.
Related Questions
With SELECT statement used for joins, the USING subclause produces …………… join.
- Equi-join
- Natural
- Left Join
- Right Join
With SELECT statement used for joins, the ON subclause produces …………… join.
- Equi-join
- Natural
- Left Join
- Right Join
What is the correct statement for describing the INTERSECT operation?
- It returns the common values from the results of any two different queries
- It returns the common rows of two different queries which have the same set of attributes in the select clause
- It returns the common rows of two different queries which have the same condition in the where clause
- None of these
What is the correct statement for describing the EXCEPT operation ?
- It excludes all the rows present in both the queries
- It includes the rows of the second query but excludes the results of the first query
- It includes the rows of the first query but excludes the results of the second query
- It includes all the rows of both queries but removes duplicates