如何实现MongoDB $ or查询？
MongoDB中$or查询的语法如下-
db.yourCollectionName.find({ $or : [ { "yourFieldName" : "yourValue1" }, {"yourFieldName":"yourValue2"},...........N ] } ).pretty();为了理解这个概念，让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.orDemo.insertOne({"UserName":"Larry","UserAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9491fd4cf1f7a64fa4df4c")
}
> db.orDemo.insertOne({"UserName":"David","UserAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9492074cf1f7a64fa4df4d")
}
> db.orDemo.insertOne({"UserName":"Mike","UserAge":25});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c94920e4cf1f7a64fa4df4e")
}
> db.orDemo.insertOne({"UserName":"Sam","UserAge":20});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9492144cf1f7a64fa4df4f")
}
> db.orDemo.insertOne({"UserName":"Carol","UserAge":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c94921d4cf1f7a64fa4df50")
}
> db.orDemo.insertOne({"UserName":"Bob","UserAge":22});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c94922c4cf1f7a64fa4df51")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.orDemo.find().pretty();
以下是输出：
{
"_id" : ObjectId("5c9491fd4cf1f7a64fa4df4c"),
"UserName" : "Larry",
"UserAge" : 23
}
{
"_id" : ObjectId("5c9492074cf1f7a64fa4df4d"),
"UserName" : "David",
"UserAge" : 21
}
{
"_id" : ObjectId("5c94920e4cf1f7a64fa4df4e"),
"UserName" : "Mike",
"UserAge" : 25
}
{
"_id" : ObjectId("5c9492144cf1f7a64fa4df4f"),
"UserName" : "Sam",
"UserAge" : 20
}
{
"_id" : ObjectId("5c94921d4cf1f7a64fa4df50"),
"UserName" : "Carol",
"UserAge" : 24
}
{
"_id" : ObjectId("5c94922c4cf1f7a64fa4df51"),
"UserName" : "Bob",
"UserAge" : 22
}这是对$or的查询-
> db.orDemo.find({ $or : [ { "UserName" : "Carol" }, {"UserName":"Larry"} ] } ).pretty();以下是输出：
{
"_id" : ObjectId("5c9491fd4cf1f7a64fa4df4c"),
"UserName" : "Larry",
"UserAge" : 23
}
{
"_id" : ObjectId("5c94921d4cf1f7a64fa4df50"),
"UserName" : "Carol",
"UserAge" : 24
}