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法律研究在 MongoDB 中查找大于特定长度的字符串？
要在 MongoDB 中查找长度大于特定值字符串，请使用 $where 运算符。语法如下 −
db.yourCollectionName.find({$where:'this.yourStringFieldName.length >
yourIntegerValue'}).pretty();为了理解上述概念，我们使用文档创建一个集合。创建一个带有文档的集合的查询如下 −
> db.stringFieldLengthDemo.insertOne({"UserId":1,"UserName":"Adam Smith"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bb4b2386c62d05142a78")
}
> db.stringFieldLengthDemo.insertOne({"UserId":2,"UserName":"Carol Taylor"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bb562386c62d05142a79")
}
> db.stringFieldLengthDemo.insertOne({"UserId":3,"UserName":"James Brown"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bb5b2386c62d05142a7a")
}
> db.stringFieldLengthDemo.insertOne({"UserId":4,"UserName":"John Smith"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bb662386c62d05142a7b")
}
> db.stringFieldLengthDemo.insertOne({"UserId":5,"UserName":"David Miller"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bb892386c62d05142a7c")
}
> db.stringFieldLengthDemo.insertOne({"UserId":6,"UserName":"John Williams"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bbb02386c62d05142a7d")
}
> db.stringFieldLengthDemo.insertOne({"UserId":7,"UserName":"Chris Evans"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77bbd32386c62d05142a7e")
}使用 find() 方法从集合中显示所有文档。查询如下 −
> db.stringFieldLengthDemo.find().pretty();
以下是输出 −
{
"_id" : ObjectId("5c77bb4b2386c62d05142a78"),
"UserId" : 1,
"UserName" : "Adam Smith"
}
{
"_id" : ObjectId("5c77bb562386c62d05142a79"),
"UserId" : 2,
"UserName" : "Carol Taylor"
}
{
"_id" : ObjectId("5c77bb5b2386c62d05142a7a"),
"UserId" : 3,
"UserName" : "James Brown"
}
{
"_id" : ObjectId("5c77bb662386c62d05142a7b"),
"UserId" : 4,
"UserName" : "John Smith"
}
{
"_id" : ObjectId("5c77bb892386c62d05142a7c"),
"UserId" : 5,
"UserName" : "David Miller"
}
{
"_id" : ObjectId("5c77bbb02386c62d05142a7d"),
"UserId" : 6,
"UserName" : "John Williams"
}
{
"_id" : ObjectId("5c77bbd32386c62d05142a7e"),
"UserId" : 7,
"UserName" : "Chris Evans"
}以下是用于查找在 MongoDB 中长度大于特定长度（例如 11）的字符串的查询 −
> db.stringFieldLengthDemo.find({$where:'this.UserName.length >11'}).pretty();以下是输出 −
{
"_id" : ObjectId("5c77bb562386c62d05142a79"),
"UserId" : 2,
"UserName" : "Carol Taylor"
}
{
"_id" : ObjectId("5c77bb892386c62d05142a7c"),
"UserId" : 5,
"UserName" : "David Miller"
}
{
"_id" : ObjectId("5c77bbb02386c62d05142a7d"),
"UserId" : 6,
"UserName" : "John Williams"
}
更新于： 30-Jul-2019
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