We assume that you already know what components are. See Chapter 26, Components for brief information.
Some components are intermediate nodes of the graph. These are called Joiners or Transformers.
For information about Transformers see Chapter 55, Transformers. Here we will describe Joiners.
Joiners serve to join data from more data sources according to the key values.
Components can have different properties. But they also can have something in common. Some properties are common for all of them, others are common for most of the components, or they are common for Joiners only. You should learn:
We can distinguish Joiners according to how they process data. All Joiners work using key values.
Some Joiners read data from two or more input ports and join them according to the equality of key values.
ExtHashJoin joins two or more data inputs according to the equality of key values.
ExtMergeJoin joins two or more sorted data inputs according to the equality of key values.
Other Joiners read data from one input port and another data source and join them according to the equality of key values.
DBJoin joins one input data source and a database according to the equality of key values.
LookupJoin joins one input data source and a lookup table according to the equality of key values.
One Joiner joins data according to the level of conformity of key values.
ApproximativeJoin joins two sorted inputs according to the level of conformity of key values.
One Joiner joins data according to the user-defined relation of key values.
RelationalJoin joins two or more sorted data
inputs according to the user-defined relation of key values
(!=, >,
>=, <.
<=).