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What is the purpose of the SQL UNION operator?

Question

What is the purpose of the SQL UNION operator?

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Solution

The purpose of the SQL UNION operator is to combine the result sets of two or more SELECT statements. It removes duplicate rows from the results. Each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order.

Here are the steps to use the SQL UNION operator:

  1. Write the first SELECT statement.
  2. Write UNION between the first and the second SELECT statement.
  3. Write the second SELECT statement.

The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL.

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Similar Questions

What does the UNION operation automatically eliminate in SQL?

What is the purpose of the SQL UNION operator?OptionsCombines rows from two or more tables, including duplicatesCombines rows from two or more tables, removing duplicatesSorts rows in a tableDeletes rows from a table

What does the UNION operation automatically eliminate in SQL?Null values.Duplicate tuples.Relations with different schemas.Operations on virtual relations.

A UNION query is which of the following?Combines the output from multiple queries and must include the same number of columns.Combines the output from no more than two queries and must include the same number of columns.Combines the output from multiple queries and does not include the same number of columns.Combines the output from no more than two queries and does not include the same number of columns.

What is special about the union data type?Select one:a.It is named differently than other data typesb.It can hold more information than other data typesc.It allows you to group multiple like items together into a single setd.It allows the same portion of memory to be accessed as different data types

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