An IN expression determines whether a string belongs to a set of string literals or whether a number belongs to a set of number values.
The path expression must have a string or numeric value. If the path expression has a NULL value, the value of the IN expression is unknown.
In the following example, the expression is TRUE if the country is UK , but FALSE if the country is Peru.
o.country IN ('UK', 'US', 'France')
You may also use input parameters:
o.country IN ('UK', 'US', 'France', :country)