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
SQL Joins & Grouping
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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.
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With SELECT statement used for joins, the USING subclause produces …………… join.
- Equi-join
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- Right Join
With SELECT statement used for joins, the ON subclause produces …………… join.
- Equi-join
- Natural
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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