GZIP
To test if the file is proper .gz file and is not corrupted use:
gzip -t <gzipped_file_name>
gzip -t <gzipped_file_name>
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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