如何在select子句中使用Post in子句（如SQL Server）在Post子句中进行Postg
我在尝试postgresql以下查询如下：select name,author_id,count(1)， (select count(1) from names as n2 where n2.id = n1.id and t2.author_id = t1.author_id from names as n1group by name,author_id当然可以Microsoft SQL Server但是在postegresql它根本不可用。我读了它的文档，似乎可以重写为：
select name,author_id,count(1),total from names as n1,(select count(1) as total from names as n2 where n2.id = n1.id and n2.author_id = t1.author_id ) as totalgroup by name,author_id但这在postegresql返回以下错误： FROM中子查询不能引用同级别的其他关系。所以我被卡住了。谁知道我能做到这一点？
谢谢
解决方案:
我不确定我是否完全理解你的意图，但以下内容可能与你想要的非常接近：
select n1.name,n1.author_id,count_1,total_countfrom (select id,name,author_id,count(1) as count_1 from names group by id,name,author_id) n1inner join (select id,author_id,count(1) as total_count from names group by id,author_id) n2on (n2.id = n1.id and n2.author_id = n1.author_id)不幸的是，这增加了按压ID以及名称和author_id对第一个子查询进行分组的要求，我认为这不是必需的。不过，我不确定如何解决此问题，因为您需要具有可用的ID加入第二个子查询。也许其他人会提出更好的解决方案。
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