如何在Rails中编写多个COUNT（*）子查询？

如何编写子查询在这样的Rails？：如何在Rails中编写多个COUNT（*）子查询？

select 
    m.field1, 
    m.field2, 
    (select count(*) from details1 d1 where d1.id=m.field3) as count1, 
    (select count(*) from details2 d2 where d2.id=m.field4) as count2, 
    (select count(*) from details3 d3 where d3.id=m.field5) as count3 
from 
    master m

数据库服务器是PostgreSQL的。

来源

2012-05-17 Paul

class Master < ActiveRecord::Base 
    set_table_name "master" 
end 
masters = Master.select(%Q"master.field1, master.field2, 
(select count(*) from details1 d1 where d1.id=m.field3) as count1, 
(select count(*) from details2 d2 where d2.id=m.field4) as count2, 
(select count(*) from details3 d3 where d3.id=m.field5) as count3").all

来源

2012-05-17 19:16:51

NoMethodError：未定义的方法'set_table_name”硕士：类（Rails的3.2.3） – Paul

看来这个选择本身能够接受一个任意SQL字符串。谢谢你的线索。我自己的书签：http://stackoverflow.com/questions/10374105/using-raw-sql-queries-in-rails-3-application – Paul

应该包含来自AR的继承。我会编辑我的答案。 –

如何在Rails中编写多个COUNT（*）子查询？

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