postgresql 带有 AS 别名的不明确的列引用
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Ambiguous Column Reference with an AS alias
提问by Hyman
I am unsure as to how to resolve an ambiguous column reference when using an alias.
我不确定在使用别名时如何解决不明确的列引用。
Imagine two tables, aand bthat both have a namecolumn. If I join these two tables and alias the result, I do not know how to reference the namecolumn for both tables. I've tried out a few variants, but none of them work:
想象两个表，a并且b都有一name列。如果我加入这两个表并为结果设置别名，我不知道如何引用这name两个表的列。我尝试了一些变体，但它们都不起作用：
Attempt 1
尝试 1
SELECT a.name, b.name
FROM (a INNER JOIN b ON a.id = b.id) AS x
This doesn't work as aand bare out of scope.
这不起作用a并且b超出了范围。
Attempt 2
尝试 2
SELECT x.a.name, x.b.name
FROM (a INNER JOIN b ON a.id = b.id) AS x
SQL syntax doesn't work like that.
SQL 语法不是那样工作的。
Attempt 3
尝试 3
SELECT x.name, x.name
FROM (a INNER JOIN b ON a.id = b.id) AS x
That's just plain ambiguous!
这简直就是模棱两可！
I'm all out of ideas - any help would be much appreciated.
我完全没有想法 - 任何帮助将不胜感激。
回答by John Woo
don't enclose it with parenthesis since (a INNER JOIN b ON a.id = b.id)is not a complete query.
不要用括号括起来，因为(a INNER JOIN b ON a.id = b.id)它不是一个完整的查询。
SELECT a.name AS A_Name,
b.name AS B_Name
FROM a INNER JOIN b
ON a.id = b.id
or (assuming) if you have longer tables names and you want to make it short,
或者（假设）如果你有更长的表名并且你想缩短它，
SELECT a.name AS A_Name,
b.name AS B_Name
FROM longTableNameA a
INNER JOIN longTableNameB b
ON a.id = b.id
