如何在MongoDB中仅选择数字字符串？
让我们创建一个包含文档的集合-
> db.selectOnlyNumericDemo.insertOne({"UserId":"User101"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cbdb711de8cc557214c0e16")
}
> db.selectOnlyNumericDemo.insertOne({"UserId":"102"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cbdb716de8cc557214c0e17")
}
> db.selectOnlyNumericDemo.insertOne({"UserId":"User103"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cbdb71dde8cc557214c0e18")
}
> db.selectOnlyNumericDemo.insertOne({"UserId":"104"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cbdb725de8cc557214c0e19")
}在find()方法的帮助下显示集合中的所有文档-
> db.selectOnlyNumericDemo.find().pretty();
这将产生以下输出-
{ "_id" : ObjectId("5cbdb711de8cc557214c0e16"), "UserId" : "User101" }
{ "_id" : ObjectId("5cbdb716de8cc557214c0e17"), "UserId" : "102" }
{ "_id" : ObjectId("5cbdb71dde8cc557214c0e18"), "UserId" : "User103" }
{ "_id" : ObjectId("5cbdb725de8cc557214c0e19"), "UserId" : "104" }以下是仅选择数字字符串或在MongoDB中检查字符串是否为数字的查询-
> db.selectOnlyNumericDemo.find({'UserId': /^\d+$/});这将产生以下输出-
{ "_id" : ObjectId("5cbdb716de8cc557214c0e17"), "UserId" : "102" }
{ "_id" : ObjectId("5cbdb725de8cc557214c0e19"), "UserId" : "104" }