SqlResultSetMapping columns as and entities

Question

I am really confused, how does column resultset mapping work? What am I mapping when I use columns instead of entities? Look at this example...

Query q = e         


        

Answer 1

You map 4 fields from result set to 2 Java classes: first class is Order entity, and the second is (probably) String that shall contain "item_name" db field.

DB:                         Java
---                         ----
order_id              --->  \
order_quantity        --->  Order entity
order_item            --->  /
item_name             --->  String

In order to read the query results:

for (Object[] record : query.getResultList()) {
   Order order = (Order)record[0];
   String itemName = (String)record[1];
}