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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.

EXAMPLE:

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 )

fully equivalent:

(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'