How To Use The Union Block
The Union block, also known as the Combine block, simply appends data sets together (inserts rows into the table). With this block, you can union together as many data sets as you'd like - for each additional data set connected, a new input node is added to the block.
If the schema for the tables is not the same, the table will be widened to include the new columns and missing values will be set to null.
If your tables have the same structure but different column names, use a Calculation block to standardize the column names before connecting to the Union block.
1. First, add your data sources to the Canvas and then drag and drop the “Union” block. The data sources should have the same schema as you will combine them into one table.
2. Initially, the Union block will have two input nodes. With each new data source connected to the block, a new node will become available.
3. Click on the input node of the “Union” block to see the data coming in. This helps you be sure you’re sending the correct information.
4. Select the block by clicking on the center of it. You will see a message in the bottom part of the screen, letting you know that "The union block combines multiple input tables into one. Any columns that don't exist in all inputs have null values." That means there is no configuration required for this block; only one action can happen.
5. Click on the output node to see how the data looks. In our example, the data from both sheets were combined in one table, and we can see both sets of data in the section at the bottom of the screen.