8. The computer program product of claim 5 , wherein the specified data type is an integer data type.
5. A computer program product for processing hierarchical data in a relational database, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a device to cause the device to perform a method comprising: receiving, by a device, an input parameter in an initial query for querying an array in a hierarchical data object stored in a table of a relational database; transforming, by the device, the initial query into a transformed query configured to place all elements of the array into a different table and to apply a sub-query against the table for the input parameter; explicitly typecasting, by the device, the elements of the array to a specified data type and responding to a failure of the typecasting by returning, by the device, a NULL value to the relational engine, and limiting, by the device, a character size of the elements of the array to a specified width and responding to an element of the array having a character size that exceeds the specified width by returning, by the device, a NULL value to the relational engine; applying, by the device, predicate evaluation logic of a relational engine of the relational database to the transformed query; mapping, by the device, the transformed query to the initial query; and, responsive to receiving a subsequent instance of the initial query, referring, by the device, to the mapping to replace the initial query with the transformed query and subsequently applying the predicate evaluation logic of the relational engine to the transformed query.