执行MongoDB数组串联以串联记录
对于数组串联，请使用$concatArrays运算符。首先让我们创建一个包含文档的集合-
>db.arrayConcatenationDemo.insertOne({"TeacherName":["Chris","Robert"],"StudentName":["Mike","Sam"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce921c078f00858fb12e911")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.arrayConcatenationDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5ce921c078f00858fb12e911"),
"TeacherName" : [
"Chris",
"Robert"
],
"StudentName" : [
"Mike",
"Sam"
]
}以下是数组连接的查询-
> db.arrayConcatenationDemo.aggregate([
{ "$project": {
"StudentAndTeacherName": { "$concatArrays": [ "$TeacherName", "$StudentName" ] }
}}
]);这将产生以下输出-
{ "_id" : ObjectId("5ce921c078f00858fb12e911"), "StudentAndTeacherName" : [ "Chris", "Robert", "Mike", "Sam" ] }