SQL UNION Operator – Unification of Sets with Example

By | 18. 1. 2020

UNION operator makes it possible to connect 2 results of query and remove all existing duplicities in them. In other words, operator actually performs DISTINCT in final unification of records.

Syntax

SELECT Column
FROM dbo.Table
WHERE Condition

     UNION

SELECT Column
FROM dbo.Table
WHERE Condition;

Syntax is same as in all Set operators. Result of unification is all records from both tables – If there is a column (or columns) with identical value in both tables, only unique value will be the result.

(!!!) UNION Operator performs unification and removes duplicities

UNION Example

Let’s have a table with a list of products

SQL UNION

We will perform unification of 2 queries to demonstrate my point:

  • first query – records where Product Key (Primary key) is lower than 10
  • second query – records where Product Key (Primary key) is lower than 5

Script:

SELECT [ProductKey], [EnglishProductName]
FROM [AdventureWorksDW2014].[dbo].[DimProduct]
WHERE [ProductKey]<=10

      UNION

SELECT [ProductKey], [EnglishProductName]
FROM [AdventureWorksDW2014].[dbo].[DimProduct]
WHERE [ProductKey]<=5;

Script result:

SQL UNION Výsledek

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Category: SQL Operators

About Jan Zedníček

My name is Jan Zedníček and I work as a freelancer. I have been working as a freelancer for many companies for more than 5 years. I used to work as a financial controller, analyst and manager at many different companies in field of banking and manufacturing. When I am not at work, I like playing volleyball, chess, doing a workout in the gym and I enjoy tasting of best quality rums. I am trying to summarize all my knowledge on this website not to forget them (because of the rum effect, you know =) and to put them forward to anyone. Don´t worry about asking for help or writing some comments.

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