Suppose you have two table
Boys
- Name
- Age
Girls
- Name
- Age
Now lets say we want to a query that returns all Boys and Girls. Most of us who come from Oracle/SqlServer/MySql etc world will write following query
select name, age from Boys
union all
select name, age from Girls
This query will throw an error in Hive and it will look like UNION ALL does not works in Hive. UNION ALL does works in Hive, the only trick is to enclose the UNION ALL tables in a subquery, i.e. write the above as
select name, age from (
select name, age from Boys
union all
select name, age from Girls
) BoysAndGirls
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