JOIN vs UNION in Tableau
When working with data in Tableau, there are several ways to combine or merge tables together. Two of the most common methods are using JOIN and UNION operations. Although both of these operations can be used to combine tables, they are used in different situations and have different functionalities.
JOIN is a type of operation that combines rows from two or more tables based on a related column between them. There are different types of joins in Tableau, including inner join, left join, right join, and full outer join. Inner join returns only the rows that have matching values in both tables. Left join returns all the rows from the left table and matching rows from the right table. Right join returns all the rows from the right table and matching rows from the left table. Full outer join returns all the rows from both tables, and where there is no match, NULL values are returned.
UNION is a type of operation that combines the rows from two or more tables into a single table, with the same number and order of columns. The tables should have the same schema or structure, and the columns should be in the same order with the same data types. The UNION operation removes duplicate rows by default, and it appends the rows from the second table to the rows of the first table.
In summary, JOIN operation is used when you want to combine two or more tables based on a related column, and you want to see the matched and unmatched rows between the tables. UNION operation, on the other hand, is used when you want to append the rows of two or more tables that have the same schema or structure, and you want to remove duplicates. By understanding the differences between JOIN and UNION operations, you can use them effectively to combine and analyze your data in Tableau.