Union Introduction

Introduction

A Union of 2 or more tables allows you to combine rows from different tables into a single result set or โ€œstackโ€ tables one on another. In this tutorial, we will discuss the concept of union and provide an example to illustrate the process.

An Overview

Tabula Union works similarly to the SQL UNION operator, but with more flexibility. It can combine tables that have different column sets by matching columns based on their names and data types. The column order in the original tables does not matter. This feature makes union tables a powerful tool for merging data from various sources with varying structures.

Example.

Consider the following two tables:

Table A:

idnameagecountry

1

John Smith

34

USA

2

Jane Doe

28

UK

Table B:

countryidcityname

USA

3

Los Angeles

Mike Brown

UK

4

London

Emma Watson

Although the columns in both tables are not in the same order, the union tool can combine them based on the matching column names and data types.

Result:

idnameagecountrycity

1

John Smith

34

USA

NULL

2

Jane Doe

28

UK

NULL

3

Mike Brown

NULL

USA

Los Angeles

4

Emma Watson

NULL

UK

London

In the resulting union table, the matched columns (id, name, and country) are combined, while the columns with no match in the other table (age and city) are filled with NULL values.

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