Question

Stack Overflow的新手（以及一般的编码）。

我做了一些研究，但无法找到以下问题的答案：

如何将两个表连接到应用于维度的函数结果，而不是维度本身？

即。我想在函数lower（）的小写结果上加入以下两个表，而不是像它们一样加入大小写不明确的维度。

SELECT
lower(first_name) as firstname
,lower(last_name) as lastname
,lower(email) as email1
,total_donated
From BensData.Donations As a

JOIN EACH

(Select
lower(first_name) as first
,lower(last_name) as last
,lower(email) as email2
,sum(amount) as total_donated
From BensData.Donations 
GROUP BY email2, first, last) As b

ON a.email1=b.email2 AND a.firstname=b.first AND a.lastname=b.last

它不允许我加入我在第一个表（a）中创建的别名，但是，如果我在表a（first_name和last_name）中加入ON原始维度，那么结果将基于大小写不明确的维度，并给出不希望的结果。

我希望这很清楚。

感谢您的帮助！

Answer 1

尝试使用两个子查询：

SELECT
a.firstname
,a.lastname
,a.email1
,a.total_donated
FROM

(SELECT
lower(first_name) as firstname
,lower(last_name) as lastname
,lower(email) as email1
,total_donated
From BensData.Donations) As a

JOIN EACH

(Select
lower(first_name) as first
,lower(last_name) as last
,lower(email) as email2
,sum(amount) as total_donated
From BensData.Donations 
GROUP BY email2, first, last) As b

ON a.email1=b.email2 AND a.firstname=b.first AND a.lastname=b.last

在原始查询中，a只是BensData.Donations的别名，因此您只能加入该表中的字段。

Answer 2

我从来没有听说过join each，也没有记录为MySQL连接的语法（见这里）。

试试这个from条款：

From BensData.Donations a JOIN
     (Select lower(first_name) as first, lower(last_name) as last,
             sum(amount) as total_donated
      From BensData.Donations 
      GROUP BY first, last
     ) b
     ON a.firstname = b.first AND a.lastname = b.last

您的版本在列之间的子查询中也缺少逗号。

为清楚起见，您应该将from子句写为：

     ON lower(a.firstname) = b.first AND lower(a.lastname) = b.last

或从子查询中删除lower()。否则，您依赖于服务器，数据库和表的默认排序规则，以了解on子句的实际内容。

Answer 3

感谢大家的帮助！

特别是指向我正确方向的链轮！他和我的代码的主要区别在于我没有在第一个SELECT子句的每个维度的前面附加表别名（例如** a。** fistname，** a。** lastname，--- - ＆gt;名字，姓氏）

由于某些原因，BigQuery因为表别名而一直给我一个错误。

这是有效的代码。

SELECT
firstname
,lastname
,email1
,total_donated
FROM

(SELECT
lower(first_name) as firstname
,lower(last_name) as lastname
,lower(email) as email1
From BensData.Donations) As a

JOIN EACH

(Select
lower(first_name) as first
,lower(last_name) as last
,lower(email) as email2
,sum(float(amount)) as total_donated
From BensData.Donations 
GROUP BY email2, first, last) As b

ON a.email1=b.email2 AND a.firstname=b.first AND a.lastname=b.last

感谢大家的帮助！

在JOIN的ON子句中使用别名

3 个答案: