标签：class creat exce pil pre while 去重 必须 led
union all
union
相同点 是 相当于上下拼接 上下两个拼接表必须字段保持一致
不同 union有去重效果，速度会更慢。
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union all的子句里不支持orderByClause、clusterByClause、distributeByClause、sortByClause或limitClause
解决：改造hql，去掉union all子查询里的orderByClause、clusterByClause、distributeByClause、sortByClause和limitClause语句
示例：select t.id from (select dummy from default.dual limit 1 union all select dummy from default.dual limit 1)t;
去掉两个子查询里的limit 1;
create table lk3 (id string,nname string,grade int,goldUser int); insert into lk3 values (1,‘jack‘,300, 10 ), (2,‘mach‘, 200, 10 ), (3,‘lich‘, 100 ,10 ), (4,‘rock‘, 1, 0 ), (5,‘mick‘, 1 ,10 ), (6,‘kight‘, 0 ,10 ), (7,‘babaya‘, 0, 0 ), (8,‘kano‘, 0, 10);
select * from lk3; +---------+------------+------------+---------------+--+ | lk3.id | lk3.nname | lk3.grade | lk3.golduser | +---------+------------+------------+---------------+--+ | 1 | jack | 300 | 10 | | 2 | mach | 200 | 10 | | 3 | lich | 100 | 10 | | 4 | rock | 1 | 0 | | 5 | mick | 1 | 10 | | 6 | kight | 0 | 10 | | 7 | babaya | 0 | 0 | | 8 | kano | 0 | 10 | +---------+------------+------------+---------------+--+
报错代码：
0: jdbc:hive2://localhost:10000> SELECT * FROM lk3 where grade != 1 order by grade desc,goldUser . . . . . . . . . . . . . . . .> union all . . . . . . . . . . . . . . . .> select * from lk3 where grade != 1 order by grade desc,goldUser; Error: Error while compiling statement: FAILED: ParseException line 3:63 Failed to recognize predicate ‘<EOF>‘.
Failed rule: ‘orderByClause clusterByClause distributeByClause sortByClause limitClause can only be applied to the whole union.‘ in statement (state=42000,code=40000)
正确处理
0: jdbc:hive2://localhost:10000> select * from (SELECT * FROM lk3 where grade != 1 order by grade desc,goldUser limit 1) a . . . . . . . . . . . . . . . .> union all . . . . . . . . . . . . . . . .> select * from lk3 where grade != 1 order by grade desc,goldUser limit 2,3; WARNING: Hive-on-MR is deprecated in Hive 2 and may not be available in the future versions. Consider using a different execution engine (i.e. spark, tez) or using Hive 1.X releases. +--------+-----------+-----------+--------------+--+ | u1.id | u1.nname | u1.grade | u1.golduser | +--------+-----------+-----------+--------------+--+ | 2 | mach | 200 | 10 | | 3 | lich | 100 | 10 | | 7 | babaya | 0 | 0 | +--------+-----------+-----------+--------------+--+ 3 rows selected (33.439 seconds)
union不支持orderByClause、clusterByClause、distributeByClause、sortByClause或limitClause
标签：class creat exce pil pre while 去重 必须 led
原文地址：https://www.cnblogs.com/wqbin/p/10289900.html
