如何根据字段的值进行排序？(how to sorting according to the value of a field? mongo)

如何根据字段的值进行排序？(how to sorting according to the value of a field? mongo)

我有一组数据。 当我选择过滤条件时，我想查询所有数据并将符合筛选条件的值显示在查询结果的前面。

例如

[ {color: 'blue', name: 'four'}, {color: 'green', name: 'five'}, {color: 'red', name: 'one'}, {color: 'red', name: 'two'}, {color: 'red', name: 'three'} ]

当我选择color:red ，并限制4，我想获得数据

[ {color: 'red', name: 'one'}, {color: 'red', name: 'two'}, {color: 'red', name: 'three'}, {color .........}// the fourth of data are not concerned for now ]

当我选择color:blue ，并限制4，我想获得数据

[ {color: 'blue', name: 'four'}, {color ........}, {color ........}, {color .........}// now just care the first data ]

有一些功能来实现这一目标？

我的英语很差，我希望其意思很清楚。

不管怎样，谢谢！

I have a set of data. When I select the filter conditions, I want to query all the data and put the values that conform to the screening conditions to display in front of the query results.

for example

[ {color: 'blue', name: 'four'}, {color: 'green', name: 'five'}, {color: 'red', name: 'one'}, {color: 'red', name: 'two'}, {color: 'red', name: 'three'} ]

when i choose color:red, and limit 4, I want to get the data

[ {color: 'red', name: 'one'}, {color: 'red', name: 'two'}, {color: 'red', name: 'three'}, {color .........}// the fourth of data are not concerned for now ]

and when i choose color:blue, and limit 4, I want to get the data

[ {color: 'blue', name: 'four'}, {color ........}, {color ........}, {color .........}// now just care the first data ]

Have some function to achieve this？

My english is so poor, I hope the meaning is clear.

anyway, thanks!

最满意答案

在您的具体示例中，您可以这样写：

db.color.aggregate([{ $addFields : { "rank" : { // add a field called rank to all our documents $cond: { if: { $eq: [ "$color", "blue" ] }, // if the color value matches "blue" then: 0, // then we want items to be on the top else: 1 // else we want them to be in the second part } } } }, { $sort : {"rank" : 1} // sort ascending by our newly created "rank" field }])

如果您使用的是旧版本的MongoDB（<3.4），它不支持$ addFields ，您可以改为使用$ project，如下所示：

db.color.aggregate([{ $project : { "color": 1, // we want to retain the value of the color field "name": 1, // the same goes for the name field "rank" : { // add a field called rank to all our documents $cond: { if: { $eq: [ "$color", "blue" ] }, // if the color value matches "blue" then: 0, // then we want items to be on the top else: 1 // else we want them to be in the second part } } } }, { $sort : {"rank" : 1} // sort ascending by our newly created "rank" field }])

In your specific example you can write this:

db.color.aggregate([{ $addFields : { "rank" : { // add a field called rank to all our documents $cond: { if: { $eq: [ "$color", "blue" ] }, // if the color value matches "blue" then: 0, // then we want items to be on the top else: 1 // else we want them to be in the second part } } } }, { $sort : {"rank" : 1} // sort ascending by our newly created "rank" field }])

If you are using an older version of MongoDB (<3.4) that does not support $addFields yet you can instead resort to using $project instead like so:

db.color.aggregate([{ $project : { "color": 1, // we want to retain the value of the color field "name": 1, // the same goes for the name field "rank" : { // add a field called rank to all our documents $cond: { if: { $eq: [ "$color", "blue" ] }, // if the color value matches "blue" then: 0, // then we want items to be on the top else: 1 // else we want them to be in the second part } } } }, { $sort : {"rank" : 1} // sort ascending by our newly created "rank" field }])