var collectiOns= ["posts", "comments", "authors"]
for (i in collections) {
doStuff(db.blog[collections[i]]);
}
db.foo.insert({"bar":"baz"})
db.users.remove()
db.mailing.list.remove({"opt-out":true})
start = time.time()
db.drop_collection("bar")
joe.relationships={"friends":joe.friends,"enimies":joe.enimies};
delete joe.friends;
delete joe.enimies;
db.users.update({"name":"joe"}, joe)
//添加或删除键值
db.users.update({"name":"joe"}, {"$set":{"favorite book":"war and peace"}})
db.users.update({"name":"joe"}, {"$unset":{"favorite book":1}})
//增减数值
db.games.update({"game":"pinball", "user":"joe"}, {"$inc":{"score":50}})
//向数组添加值
db.papers.update({"authors cited":{"$ne":"Richie"}}, {"$push":{"authors cited":"Richie"}})
//集合中增加值
db.users.update({"_id":ObjectId("xxxx")},{"$addToSet":{"emails":"xxx@126.com"}})
db.users.update({"_id":ObjectId("xxxx")},{"$addToSet":{"emails":{"$each":["xxx@126.com", "xxx@hotmail.com"]}}})
//集合中删除值
db.lists.insert("todo":["dishes","laundry","dry cleaning"])
db.lists.update({},{"$pull":{"todo":1}}) //从数组末尾删除
db.lists.update({},{"$pop":{"todo":-1}}) //从数组开头删除
//数组定位
db.blog.update({"post":post_id},{"$inc":{"comments.0.votes":1}}) //用下标
db.blog.update({"comments.author":"John"},{"$set":{"comments.$.author":"Jim"}}) //只替换第一个