Calculation of a Component: calc
Syntax
op [ calc { calcRole } calcComp := calcExpr { , { calcRole } calcComp := calcExpr }* ]
calcRole ::= identifier | measure | attribute | viral attribute
Input parameters
op |
the operand |
calcRole |
the role to ba assigned to a Component to be calculated |
calcComp |
the name of a Component to be calculated |
calcExpr |
expression at component level, having only Components of the
input Data Sets as operands, used to calculate a Component
|
Examples of valid syntaxes
DS_1 [ calc Me_3 := Me_1 + Me_2 ]
Semantics for scalar operations
This operator cannot be applied to scalar values.
Input parameters type
op
dataset
calcComp
name<component>
calcExpr
component<scalar>
Result type
result
dataset
Additional Constraints
The calcComp parameter cannot be the name of an Identifier component.
All the components used in calcComp must belong to the operand Data Set op.
Behavior
The operator calculates new Identifier, Measure or Attribute Components on the basis of sub-expressions at Component level. Each Component is calculated through an independent sub-expression. It is possible to specify the role of the calculated Component among measure, identifier, attribute, or viral attribute, therefore the calc clause can be used also to change the role of a Component when possible. The keyword viral allows controlling the virality of the calculated Attributes (for the attribute propagation rule see the User Manual). When the role is omitted, the following rule is applied: if the component exists in the operand Data Set then it maintains its role; if the component does not exist in the operand Data Set then its role is Measure.
The calcExpr sub-expressions are independent one another, they can only reference Components of the input Data Set and cannot use Components generated, for example, by other calcExpr. If the calculated Component is a new Component, it is added to the output Data Set. If the Calculated component is a Measure or an Attribute that already exists in the input Data Set, the calculated values overwrite the original values. If the calculated Component is an Identifier that already exists in the input Data Set, an exception is raised because overwriting an Identifier Component is forbidden for preserving the functional behaviour. Analytic invocations can be used in the calc clause.
Examples
Given the Data Set DS_1:
Input DS_1 (see structure)
Id_1 |
Id_2 |
Id_3 |
Me_1 |
|---|---|---|---|
1 |
A |
CA |
20 |
1 |
B |
CA |
2 |
2 |
A |
CA |
2 |
Example 1
DS_r := DS_1 [ calc Me_1:= Me_1 * 2 ];
results in (see structure):
Id_1 |
Id_2 |
Id_3 |
Me_1 |
|---|---|---|---|
1 |
A |
CA |
40 |
1 |
B |
CA |
4 |
2 |
A |
CA |
4 |
Example 2
DS_r := DS_1 [ calc attribute At_1:= "EP" ];
results in (see structure):
Id_1 |
Id_2 |
Id_3 |
Me_1 |
At_1 |
|---|---|---|---|---|
1 |
A |
CA |
20 |
EP |
1 |
B |
CA |
2 |
EP |
2 |
A |
CA |
2 |
EP |