JAXBContext
This class is the entry point for JAXB API. One must get instance of this class first and then from this instance, marshaller, unmarshaller or validator instances can be obtained.
SQL
Joins - Not always very obvious ( Following example uses Hive ). create table x_temp ( name string, p_date int ) insert into x_temp(name,p_date) values ('x1',20181025),('x2', 20181026), ('x3',20181027) create table y_temp ( name string, s_date int ) insert into y_temp(name,s_date) values ('x1',20181025),('x2', 20181026), ('x3',20181027) create table z_temp ( name string, p_date int, s_date int ) insert into z_temp(name,p_date,s_date) values ('z1','20181025','20181025') select x.*, y.* from x_temp x, y_temp y, z_temp z where x.p_date != z.p_date and y.s_date != z.s_date) generates 4 records... x.name,x.p_date,y.name,y.s_date x2, 20181026, x2, 20181026 x3, 20181027, x2, 20181026 x2, 20181026, x3, 20181027 x3, 20181027, x3, 20181027 select x.*, y.* from x_temp x, y_temp y, z_temp z where x.p_date != z.p_date or y.s_date != z.s_date) generates 8 records x.name,x.p_date,y....
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