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法律研究在 MongoDB 中查詢大於特定長度的字串？
要在 MongoDB 中查詢長度大於特定值字串，請使用 $where 運算子。語法如下 −
db.yourCollectionName.find({$where:'this.yourStringFieldName.length >
yourIntegerValue'}).pretty();為了理解上述概念，我們使用文件建立一個集合。建立一個帶有文件的集合的查詢如下 −
> 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() 方法從集合中顯示所有文件。查詢如下 −
> db.stringFieldLengthDemo.find().pretty();
以下是輸出 −
{
"_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"
}以下是用於查詢在 MongoDB 中長度大於特定長度（例如 11）的字串的查詢 −
> db.stringFieldLengthDemo.find({$where:'this.UserName.length >11'}).pretty();以下是輸出 −
{
"_id" : ObjectId("5c77bb562386c62d05142a79"),
"UserId" : 2,
"UserName" : "Carol Taylor"
}
{
"_id" : ObjectId("5c77bb892386c62d05142a7c"),
"UserId" : 5,
"UserName" : "David Miller"
}
{
"_id" : ObjectId("5c77bbb02386c62d05142a7d"),
"UserId" : 6,
"UserName" : "John Williams"
}
更新於： 30-Jul-2019
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