这在MongoDB中如何选择 [英] How does this select in MongoDB

问题描述

MongoDB中这个怎么选择

How does this select in MongoDB

select cidade 
from rendaxeducação 
where idheducacao = (
    select max(idheducacao) 
    from rendaxeducacao 
    where idh=2000
);

推荐答案

 db.rendaxeducacao.aggregate([
        {$math : {idh : 2000}                  //  fiter only where idh=2000
        },
        {$group: { _id: 1, 
                   max_idheducacao : {$max : $idheducacao}  // find max
          }
        },
        {$project:{                          //  select cidade 
               _id:0,
               cidade:1
          }  
        } 

  ])

rendaxeducao = 收藏

rendaxeducacao = collection

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