Non-persistent assignment: :=`
Syntax
re := op
Input parameters
re |
the result |
right |
the operand. According to the general VTL rule allowing the indentation of the operators,
op can be obtained through an expression as complex as needed
(for example op can be the expression
DS_1 - DS_2). |
Examples of valid syntaxes
DS_r := DS_1
DS_r := 3
DS_r := DS_1 - DS_2
DS_r := 3 + 2
Semantics for scalar operations
Empty
Input parameters type
op
dataset
| scalar
Result type
re
dataset
Additional Constraints
The assignment cannot be used at Component level because the result of a Transformation cannot be a Data Set Component. When operations at Component level are invoked, the result is the Data Set which the output Components belongs to.
The same symbol denoting the non-persistent assignment Operator (:=) is also used inside other operations at Component level (for example in calc and aggr) in order to assign the result of the operation to the output Component: please note that in these cases the symbol := does not denote the non-persistent assignment (i.e., this Operator), which cannot operate at Component level, but a special keyword of the syntax of the other Operator in which it is used.
Behaviour
The value of the operand op is assigned to the result re, which is non-persistent and therefore is not stored.
As mentioned, the operand op can be obtained through an expression as complex as needed
(for example op can be the expression DS_1 - DS_2).
The result re is a non-persistent Data Set that has the same data structure as the Operand. For example in DS_r := DS_1
the data structure of DS_r is the same as the one of DS_1.
If the Operand op is a scalar value, the result Data Set has no Components and contains only such a scalar value.
For example, income := 3 assigns the value 3 to the non-persistent Data Set named income.
Examples
Given the operand dataset DS_1:
Input DS_1 (see structure)
Id_1 |
Id_2 |
Me_1 |
Me_2 |
|---|---|---|---|
2013 |
Belgium |
5 |
5 |
2013 |
Denmark |
2 |
10 |
2013 |
France |
3 |
12 |
2013 |
Spain |
4 |
20 |
Example 1
DS_r := DS_1;
results in (see structure):
Id_1 |
Id_2 |
Me_1 |
Me_2 |
|---|---|---|---|
2013 |
Belgium |
5 |
5 |
2013 |
Denmark |
2 |
10 |
2013 |
France |
3 |
12 |
2013 |
Spain |
4 |
20 |