Database GroupBy
This node allows rows to be grouped by the selected columns from the input database table.
Within the dialog, an SQL GROUP BY clause is interactively created by selecting the columns to group by
and the columns to aggregate.
The columns to aggregate can be either defined by selecting the columns directly,
by name based on a search pattern or based on the data type. Input columns are handled in
this order and only considered once e.g. columns that are added directly on the
"Manual Aggregation" tab are ignored even if their name matches a search pattern on the
"Pattern Based Aggregation" tab or their type matches a defined type on the
"Type Based Aggregation" tab. The same holds for columns that are added based on a search pattern.
They are ignored even if they match a criterion that has been defined in the "Type Based Aggregation" tab.
The "Manual Aggregation" tab allows you to change the aggregation method of more than one
column. In order to do so select the columns to change, open the context menu with a right mouse click
and select the aggregation method to use.
In the "Pattern Based Aggregation" tab you can assign aggregation methods to columns based on a
search pattern. The pattern can be either a string with wildcards or a
regular expression.
Columns where the name matches the pattern but where the data type is not compatible with the
selected aggregation method are ignored. Only columns that have not been selected as group column or
that have not been selected as aggregation column on the "Manual Aggregation" tab are considered.
The "Type Based Aggregation" tab allows to select an aggregation method for all columns of a certain
data type e.g. to compute the mean for all numerical columns (DoubleCell). Only columns that have not
been handled by the other tabs e.g. group, column based and pattern based are considered.
The data type list to choose from contains basic types e.g String, Double, etc. and all data types
the current input table contains.
A detailed description of the available aggregation methods can be
found on the 'Description' tab in the node dialog.
Dialog Options
Groups
- Group settings
-
Select one or more column(s) according to which the group(s) is/are created.
Advanced settings
- Column naming
-
The name of the resulting aggregation column(s) depends on the
selected naming schema.
- Keep original name(s):
Keeps the original column names.
- Aggregation method (column name):
Uses the aggregation method
first and appends the column name
in brackets
- Column name (aggregation method):
Uses the column name first and
appends the aggregation method
in brackets
- Add COUNT(*)
-
Tick this option to add a column that contains the result for the COUNT(*) operation.
- column name
-
The name of the COUNT(*) column. Only enabled if the "Add COUNT(*)" option is selected.
Manual Aggregation
- Aggregation settings
-
Select one or more column(s) for aggregation from the available
columns list. Change the aggregation method in the Aggregation
column of the table. You can add the same column multiple
times. In order to change the aggregation method of more than one
column select all columns to change, open the context menu with a
right mouse click and select the aggregation method to use.
- Parameter
-
The parameter column shows an "Edit" button for all
aggregation operators that require additional information.
Clicking on the "Edit" button opens the parameter dialog
which allows changing the operator specific settings.
Pattern Based Aggregation
- Aggregation settings
-
Use the "Add" button to add a new row with a search pattern to the aggregation settings.
The search pattern can either be a string with wildcards or a
regular expression.
Supported wildcards are * (matches any number of characters) and ? (matches one character) e.g. KNI*
would match all strings that start with KNI such as KNIME whereas KNI? would match only strings that start
with KNI followed by a fourth character.
Double click the "Search pattern" cell to edit the pattern.
The cell is colored in red if the pattern is invalid.
- RegEx
- Tick this option if the search pattern is a regular expression otherwise
it is treated as string with wildcards ('*' and '?').
- Parameter
-
The parameter column shows an "Edit" button for all
aggregation operators that require additional information.
Clicking on the "Edit" button opens the parameter dialog
which allows changing the operator specific settings.
Type Based Aggregation
- Aggregation Settings
-
Select one or more data type from the available type list.
Change the aggregation method in the Aggregation
column of the table. You can add the same data type multiple
times. The list contains standard types e.g. Double, String etc. and all types of the input table.
- Parameter
-
The parameter column shows an "Edit" button for all
aggregation operators that require additional information.
Clicking on the "Edit" button opens the parameter dialog
which allows changing the operator specific settings.
Ports
Input Ports
0 |
Table in database to apply group by
|
Output Ports
0 |
Table in the database with grouped rows
|
This node is contained in KNIME Base Nodes
provided by KNIME GmbH, Konstanz, Germany.