When to add a scalar to a named query

Question

When do I need to add a scalar to a named query? For instance:

<return-scalar column="colName" type="java.lang.String" /> 

Sometimes they do not seem to be needed, and sometimes, without a scalar, the request will throw an exception.

Answer 1

Let me share some materials.

• If your query select * from the table , setScalar can be used to dynamically restrict the no column.

• If you use a scalar, the query will not use ResultSetMetadata b> to find this type and will use a faster and more efficient type.

• java.sql.Types ResultSetMetaData, Hibernate, . , registerHibernateType .