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Databases & SQL vocabulary · SQL Statements and Queries

UNION

Meaning in databases & SQL, with examples

/ˈjuːnjən/nounCommon term

In databases & SQL, UNION means: A SQL operator that stacks the results of two or more SELECT statements into one result, one under the other, removing duplicate rows.

In Turkish: birleşim, UNION

How it is used

Each SELECT must return the same number of columns with compatible types. UNION ALL keeps duplicates and is faster, because the database does not have to check for them; use it when duplicates are impossible or wanted. A join puts columns side by side; a UNION puts rows on top of each other.

Example sentences

  1. We UNION the archived orders with the current ones to build the yearly report.

  2. Switch to UNION ALL here; the two tables can't contain the same rows anyway.

Common collocations

  • UNION ALL
  • UNION of two queries
  • UNION vs JOIN
  • combine results
  • SELECT statementThe SQL statement that reads data from one or more tables and returns the matching rows without changing anything in the database.
  • SELECT DISTINCTA form of the SELECT statement that removes duplicate rows from the result, so each combination of returned values appears only once.
  • joinA SQL operation that combines rows from two or more tables using a related column, such as a customer ID. As a verb, to join tables means to combine them this way.
  • queryA request sent to a database to read or change data, usually written in SQL. As a verb, to query means to ask a database for data.

This word in other fields

The same English word can have a different meaning in another field:

More terms: SQL Statements and Queries

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