Hive UNION ALL报错Top level UNION is not supported currently

来源：四号程序员

下面只是一个例子，一般用OR 条件肯定会搞定的。

SELECT a, b from tb1 where a > 100
UNION
SELECT a, b from tb2 where a > 1000;

会报错 FAILED: SemanticException 1:62 Top level UNION is not supported currently; use a subquery for the UNION. Error encountered near token ‘””‘

正确的做法是：把所有UNION ALL子句放到sub-query中，并且给table加别名，如下：

SELECT * FROM
(
SELECT a, b from tb1 where a > 100
UNION
SELECT a, b from tb2 where a > 1000
) tmp;