Set Retention Check
It is checked whether the tested value presented in one of the given set of values. You can use IN instruction to do this.
The checked expression in the IN instruction can be any legal expression, but usually it is a field name as in the above-mentioned examples.
If NULL value is the result of checked expression, IN instruction also returns NULL.
All elements in the given values list should have the same data-type.
With the help of NOT IN instruction you can be sure that data-element is not the member of the given set.
Note. IN instruction does not extend SQL possibilities as it can be expressed as:
X IN ( A, B, C )
(X = A) OR (X = B) OR (X = C)
But IN instruction proposes much more effective way of selection condition expression, especially if set contains big amount of elements.
If set contains one element:
CITY IN ( 'New York' )
it can be replaced with the simple comparison:
CITY = 'New York'