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The UNION operator combines rows from two or more queries including duplicate rows.
The UNION operator combines rows from two or more queries including duplicate rows.
False
The relational set operators UNION, INTERSECT, and MINUS require relations to be union-compatible.
The relational set operators UNION, INTERSECT, and MINUS require relations to be union-compatible.
True
The SQL UNION operator can only be used to combine the result of two SQL SELECT queries.
The SQL UNION operator can only be used to combine the result of two SQL SELECT queries.
False
The SQL UNION operator eliminates duplicate rows from its result set.
The SQL UNION operator eliminates duplicate rows from its result set.
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The data types of the columns in the two tables on which the UNION operation is being applied must be different.
The data types of the columns in the two tables on which the UNION operation is being applied must be different.
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The UNION operator is used to unite less than two queries.
The UNION operator is used to unite less than two queries.
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The UNION operator removes duplicate rows from the result set.
The UNION operator removes duplicate rows from the result set.
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The INTERSECT operator is used to combine rows from two queries, returning only the rows that appear in both sets.
The INTERSECT operator is used to combine rows from two queries, returning only the rows that appear in both sets.
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The MINUS operator is used to combine rows from two queries, returning only the rows that appear in the first set and in the second set.
The MINUS operator is used to combine rows from two queries, returning only the rows that appear in the first set and in the second set.
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A natural join is a type of inner join operation.
A natural join is a type of inner join operation.
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The CROSS JOIN operator is used to combine rows from two tables based on a common column between them.
The CROSS JOIN operator is used to combine rows from two tables based on a common column between them.
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The IN operator can be used in place of the INTERSECT operator.
The IN operator can be used in place of the INTERSECT operator.
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The UNION operator can be used to unite more than two queries.
The UNION operator can be used to unite more than two queries.
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An inner join operation returns all rows from both tables involved in the join operation.
An inner join operation returns all rows from both tables involved in the join operation.
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Study Notes
Relational Set Operators
- Relational set operators require relations to be union-compatible, meaning named attributes must be the same and have identical data types.
- There are four types of relational set operators: UNION, UNION ALL, INTERSECT, and MINUS.
UNION
- Combines rows from two or more queries without including duplicate rows.
- Can be used to unite more than two queries.
- Eliminates duplicate rows from the result set.
UNION ALL
- Produces a relation that retains duplicate rows.
- Can be used to unite more than two queries.
INTERSECT
- Combines rows from two queries, returning only the rows that appear in both sets.
- Syntax: query INTERSECT query.
- Can be replaced with IN and NOT IN subqueries.
MINUS
- Combines rows from two queries, returning only the rows that appear in the first set but not in the second.
- Syntax: query MINUS query.
SQL Join Operators
- Join operation merges rows from two tables and returns rows based on common values or conditions.
- Types of joins: Natural join, Inner join, Outer join, and Cross join.
Cross Join
- Performs the relational product of two tables, also known as the Cartesian product.
- Syntax: SELECT column-list FROM table1 CROSS JOIN table2.
MySQL Natural Join
- Combines rows of two or more tables based on a common column between them.
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Description
Learn about relational set operators, advanced SQL JOIN syntax, subqueries, correlated queries, and SQL functions for data manipulation in this chapter of Database Systems, 8th Edition.
