Question

考虑两个表，ratings和products，并且有一些列。我正在尝试使用

查询一些数据

SELECT AVG(r.rating), COUNT(p.prod_id) FROM ratings as r, products as p;

我保存为script.impala并使用impala-shell -f script.impala保存。我得到以下内容：

[user@localhost]$ impala-shell -f script.impala *mumble* Query: select AVG(r.rating), COUNT(p.prod_id) FROM ratings as r, products as p ERROR: NotImplementedException: Join between 'r' and 'p' requires at least one conjunctive equality predicate between the two tables Could not execute command: select AVG(r.rating), COUNT(p.prod_id) FROM ratings as r, products as p

我在Impala docs中找不到关于此类查询的任何信息。这个查询的正确语法是什么？两者都完全适用于单独的陈述。

Impala版本为Impala Shell v1.0 (d1bf0d1) built on Sun Apr 28 15:33:52 PDT 2013。我知道它已经超级老了，但我无法改变它。

Answer 1

从不在FROM子句中使用逗号。始终使用正确的，明确的JOIN语法。在您的情况下，您有一个查询。怎么样？

select r.avg_rating), p.cnt_products
from (select avg(r.rating) as avg_rating from ratings r) cross join
     (select count(*) as cnt_products from products p);

无论如何，您的查询将会返回非感性结果。例如，它将返回两个表中行数的乘积。

使用Impala的Conjuctive查询

1 个答案: