A join reads data from multiple sources and builds a single data table that is passed to the next operation. The type of join can be specified in the configuration.

To better explain the Join operation, here is a small example:

There is the following data in an Excel table:

Id	Name	Color
1	Pants	red
2	blouse	green
3	shirt	red
4	T-shirt	blue

1. create join

A flow has already been created and the Excel table has been created as data source with the name ‘Main Table’.

Now, in the graphical flow editor, the ‘Join’ operation is dragged and dropped onto the surface. Now the data source has to be connected to the join.

2. configure join

After the input, the configuration for the join appears. The following items can be configured:

1. Name of the join - changes to the name of the join are made here.
2. Key attributes - main source The key attribute from the main source on belongs here.
3. data table as second source` - if this switch is selected, a data table can be created in advance, under the menu item data tables, can be selected.
4. key attribute of the secondary source - selection of the key for the secondary source.
5. second source attribute prefix - define a prefix for the second source attributes.
6. multivalue merge - multiple values for a key attribute can be merged into one list.

For the example, the data structure for the secondary source is as follows:

name	purchase price	sale price
shirt	1,98	19,99
shirt	1,76	17,98
shirt	2,12	24,49
blouse	5,9	fifty-nine
pants	5,67	thirty

The following settings are required for this:

• Key attribute of secondary source as ‘name’.
• Prefix gets the value ’NEW
• Switch on multivalue merge

With the button ‘Join’ the operation can be executed:

3. result of the join

The following result is now displayed in the result view for the join:

Multivalue Merge on

Id	color	name	new_purchase_price	new_sale_price
1	red	pants	5,67	thirty
2	green	blouse	5,9	fifty-nine
3	red	shirt	[1.98, 1.76, 2.12]	[10.98, 17.98, 24.99]
4	blue	shirt	undefined	undefined

• The shirt with the red color has combined prices from the second table.
• The blue shirt gets the value ‘undefined’ for undefined because the values are not present in the secondary table.

Multivalue Merge off

Id	Color	Name	New_PurchasePrice	New_SalePrice
1	red	pants	5,67	thirty
2	green	blouse	5,9	fifty-nine
3	red	shirt	2.12	24,99
4	blue	t-shirt	undefined	undefined

• The shirt with the red color has the last found price from the secondary table.