将sql query转换为Mongo languague [英] Translation of sql query to Mongo languague
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问题描述
我正在尝试在Mongo中执行以下查询:
I am trying to do the following query in Mongo:
SELECT *
FROM events
WHERE v1 - v2 > 20;
其中v1和v2是SQL DB中的列名称.
where v1 and v2 are names of columns in the SQL DB.
如何将其翻译成Mongo Languague?
how can I translate it to Mongo Languague?
推荐答案
假定您在events
中有这些文档:
Assume you have these documents in your events
:
{
"_id" : ObjectId("54cdfde528bb923955eff8b4"),
"v1" : 35,
"v2" : 10
}
/* 1 */
{
"_id" : ObjectId("54cdfde928bb923955eff8b5"),
"v1" : 10,
"v2" : 20
}
您不能使用简单的find()
查询.您应该使用聚合:
You cant use a simple find()
query. You should use aggregation:
db.events.aggregate(
[
{ $project : { 'diff' : { $subtract : ['$v1', '$v2'] }, v1 : 1, v2 : 1 } },
{ $match : { diff : { $gt : 20} } },
{ $project : { v1 : 1, v2 : 1 } },
]).result
结果是:
{
"0" : {
"_id" : ObjectId("54cdfde528bb923955eff8b4"),
"v1" : 35,
"v2" : 10
}
}
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