distinct

distinct用来找出给定键的所有不同值。使用时必须指定集合和键。

db.runCommand({"distinct":"people","key":"age"})

假设集合中有如下文档

{name:"Ada",age:20}
{name:"Fred",age:35}
{name:"Susan",age:60}
{name:"Andy",age:35}

如果对"age"键使用distinct，会得到所有不同的年龄：

{"values":[20,35,60],"ok":1}