In this article:
Join
The Join transformer is an object that is used join data from several providers into one data consumer by means of identification and selection of unique records and further transfer of data according to the specified links between data provider fields and data consumer field.
This transformer can be used to get in the output set only the records, which are contained in all data providers or all records of one data provider appended with values from other providers. The selected connection determines which selection algorithm will be used.
To identify records, all data providers must have indexes determined. The list of fields and and their types in indexes must match. Values of the fields added to the index will be used to search and determine the records, which should be loaded to data consumer.
NOTE. Objects, on which data providers are based, can have a different number and types of indexes. They do not affect record selection in the Join transformer.
The Join transformer works more effectively if the following conditions are satisfied:
Data providers cannot contain duplicates with the same unique index.
Field order in the unique index must match in all data providers.
When the Join transformer with the External Connection type is used from the tables:
| Key | Date | Value |
| 1 | Summer | 2222 |
| 2 | Winter | 4444 |
| 3 | Spring | 5555 |
and:
| Key | Date | Value2 |
| 1 | Summer | 1111 |
| 2 | Winter | 3333 |
it can be converted to the following table:
| Key | Date | Value | Value2 |
| 1 | Summer | 2222 | 1111 |
| 2 | Winter | 4444 | 3333 |
| 3 | Spring | 5555 |
Connection Type
The page is used to determine a connection type.
The following connection types are available:
Internal Connection. The consumer object gets only those records of the provider objects that have matching values of indexed fields.
External Connection. The consumer object gets all records from the provider specified in the Main Input field, data from other providers complete them. Provider objects are linked by a specified index.
Edit Output
The Edit Output page enables the user to set links to the consumer object, to which data on executing ETL tasks is loaded.
NOTE. The page is common to all data connectors and transformers, except for the Split and User Algorithm transformers. Consider setting up a list of fields and output links using the example of the Repository data source editing wizard.
The following settings are available on the page:
Identifier
Browse button.
Up and 
Down buttons.Edit Output with Error Records
The Edit Output with Error Records page is used to set links to the consumer object, to which information about error records skipped by the transformer is exported.
NOTE. The page is common to all data transformers, except for the Union and User Algorithm transformers. Consider setting up a list of fields and output links using the example of the Split data transformer editing wizard.
The following settings are available on the page:
Index
The Index page is used to determine indexed fields for each of the inputs. Provider data is mapped by the values of indexed fields.
To select an indexed field:
Drag the selected field from the Source Fields list to corresponding input in the Selected Fields list.
Select a field in the Source Fields list and an input in the Selected Fields list. Click the Add button.
When going to the next page the user is prompted to fill in the list of fields from the linked output.
Fields Linking
Set correspondence between input and output fields on the Fields Linking page.
Operations with field links:
Automatic creation of field links. It enables the user to create automatically links between all input and output fields with matching identifiers. Click the Automatically button to create links automatically.
Creation of field links. It enables the user to link input and output fields with different identifiers. To create a link, drag the required field from the Source Fields area to the Input and Output Fields Mapping area.
Editing of field links. It enables the user to edit transformation formula of output value using editor. To edit link in the Input and Output Fields Mapping area:
Select the required link and click the Edit button.
Double-click the required link with the main mouse button.
Deletion of links. To delete link between input and output fields, click the Clear button.