Field Operations and Joins

In Tableau, combining data from different tables is a common operation when working with datasets. This process is achieved using joins, which combine rows from two tables by matching them based on a shared field, called a key. Joins are particularly useful for enriching data analysis by bringing together related information, such as linking customer details with order history or integrating regional sales data with product performance.

In this video, we'll focus on left join. A left join includes all rows from the left table, along with matching rows from the right table. If there are no matching rows in the right table, Tableau displays blanks (NULL). This approach ensures that no data is lost from the primary (left) table during the merging process.

Other Join Types

• Inner Join: includes only rows where the key field values match in both tables. Rows without matches are excluded from the result;
• Right Join: includes all rows from the right table, along with matching rows from the left table. For rows with no match in the left table, Tableau displays blanks (NULL);
• Full Outer Join: includes all rows from both tables. When a match exists, Tableau combines the rows. If no match exists, blanks (NULL) fill in for the missing values from the other table.

The illustration below clarifies the joins (A and B represent specific tables, and the blue color highlights the result):