MongoDB正则表达式显示前五个字母大写的记录？
首先让我们创建一个包含文档的集合-
> db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"JOHN Smith"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7edef1a844af18acdffb2")
}
> db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"SAM Williams"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7ee011a844af18acdffb3")
}
> db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"CAROL Taylor"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7ee101a844af18acdffb4")
}
> db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"Bob Taylor"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7ee351a844af18acdffb5")
}
> db.upperCaseFiveLetterDemo.insertOne({"StudentFullName":"DAVID Miller"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd7ee451a844af18acdffb6")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.upperCaseFiveLetterDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cd7edef1a844af18acdffb2"),
"StudentFullName" : "JOHN Smith"
}
{
"_id" : ObjectId("5cd7ee011a844af18acdffb3"),
"StudentFullName" : "SAM Williams"
}
{
"_id" : ObjectId("5cd7ee101a844af18acdffb4"),
"StudentFullName" : "CAROL Taylor"
}
{
"_id" : ObjectId("5cd7ee351a844af18acdffb5"),
"StudentFullName" : "Bob Taylor"
}
{
"_id" : ObjectId("5cd7ee451a844af18acdffb6"),
"StudentFullName" : "DAVID Miller"
}以下是查询以获取前五个字母大写的记录数-
> db.upperCaseFiveLetterDemo.find({StudentFullName : {$regex : /[A-Z]{5}/ } }).count();这将产生以下输出-
2
有两个文档，前五个字母大写。现在让我们显示这些文档-
> db.upperCaseFiveLetterDemo.find({StudentFullName : {$regex : /[A-Z]{5}/ } });这将产生以下输出-
{ "_id" : ObjectId("5cd7ee101a844af18acdffb4"), "StudentFullName" : "CAROL Taylor" }
{ "_id" : ObjectId("5cd7ee451a844af18acdffb6"), "StudentFullName" : "DAVID Miller" }