What is the FeatureJoiner?
The FeatureJoiner transformer is new for FME 2018. It's a SQL-based alternative to the FeatureMerger transformer, that joins data together on the basis of common keys and using SQL terminology to define the results.
On the canvas it looks like this:
And the parameters dialog looks like this:
Join Modes
Joined features exit the transformer through the Joined port. What happens to the remaining features is controlled by the Join Mode parameter.
There are three join modes: Inner, Left, and Full.
In Inner mode features without a join exit through either the Unjoined Left or Unjoined Right port.
In Left mode, Left features without a match still exit through the Joined port. Right features without a match exit the Unjoined Right port.
In Full mode, both Left and Right features without a match still exit through the Joined port.
We can visualize this behaviour with a diagram:
| Mode | Description | Depiction | Joined Output | Unjoined Left | Unjoined Right |
|---|---|---|---|---|---|
| Left | Left features look for a match and are output whether they find a match or not |  | All matches plus unmatched Left features | None | Unused Right features |
| Inner | Left features look for a match and are output if they find one |  | All matches only | Unmatched Left features | Unused Right features |
| Full | Both Left and Right features output through the Joined output port, whether they find a join or not |  | All matches plus unmatched Left and Right features | None | None |