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Questions and Answers
What is the main purpose of an outer join in relational databases?
What is the main purpose of an outer join in relational databases?
- To prevent any loss of data in the join operation (correct)
- To combine only matching rows from two tables
- To create a new table by discarding non-matching data
- To include all records from both tables, regardless of matches
Which statement correctly describes how outer join handles unmatched tuples?
Which statement correctly describes how outer join handles unmatched tuples?
- Unmatched tuples are ignored in the final result set
- Unmatched tuples are included with null values for missing attributes (correct)
- Unmatched tuples are used to create a new subset of data
- Unmatched tuples trigger an error and stop the operation
In the context of outer joins, what does the term 'null' signify?
In the context of outer joins, what does the term 'null' signify?
- A representation of an unknown or non-existent value (correct)
- A formal way to identify duplicate records
- An indication of an error in the join operation
- A placeholder for any data type
How does an outer join differ from an inner join?
How does an outer join differ from an inner join?
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Which of the following is a direct outcome of performing an outer join?
Which of the following is a direct outcome of performing an outer join?
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Study Notes
Outer Join
- An extension of the join operation that preserves all information from both tables involved
- Avoids loss of information that happens in regular joins when a value does not have a match in the other table
- Adds tuples from a table that does not have a matching tuple in the other table to the result of the join
- Employs
nullvalues to represent the absence of a value in the tuple - Used to show all information from both tables, regardless of matches
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