MongoDB 更新修改器

更新修改器是种特殊的键，用来指定复杂的更新操作，比如调整、增加或者删除键，还可能是从操作数组或者内嵌文档.
1.$inc修改器 用来增加值。
> db.analytics.find();
{ "_id" : ObjectId("4fc39b6b57bb647e0855d6ed"), "url" : "www.baidu.com", "pagevi
ews" : 1 }
> db.analytics.update({url:"www.baidu.com"},{"$inc":{"pageviews":1}})
> db.analytics.find();
{ "_id" : ObjectId("4fc39b6b57bb647e0855d6ed"), "url" : "www.baidu.com", "pagevi
ews" : 2 }
2.$set修改器 用来指定一个键的值，如果这个键不存在，则创建它。
> db.users.find();
{ "_id" : ObjectId("4fc3a96f57bb647e0855d6ee"), "name" : "joe", "age" : 30, "sex
" : "male", "location" : "shenzhen" }
> db.users.update({"_id":ObjectId("4fc3a96f57bb647e0855d6ee")},{"$set":{"favorit
e book":"war and peace"}});
> db.users.find();
{ "_id" : ObjectId("4fc3a96f57bb647e0855d6ee"), "age" : 30, "favorite book" : "w
ar and peace", "location" : "shenzhen", "name" : "joe", "sex" : "male" }
3.数组修改器
3.1$push往数组中添加元素
> db.blog.find();
{ "_id" : ObjectId("4fa4e7e8c42348a59791e0d6"), "title" : "My Blog Post", "conte
nt" : "Here's my blog post.", "date" : "2012-12-04", "comments" : [ ] }
> db.blog.update({"title":"My Blog Post"},{"$push":{"comments":{"name":"jenny","
content":"nice post."}}})
> db.blog.findOne();
{
        "_id" : ObjectId("4fa4e7e8c42348a59791e0d6"),
        "comments" : [
                {
                        "name" : "jenny",
                        "content" : "nice post."
                }
        ],
        "content" : "Here's my blog post.",
        "date" : "2012-12-04",
        "title" : "My Blog Post"
}
3.2$addToSet可避免重复数据
db.user.update({"age":30},{"$addToSet":{"emails":"[email protected]"}})
> db.users.find();
{ "_id" : ObjectId("4fc3a96f57bb647e0855d6ee"), "age" : 30, "emails" : [ "joe@gm
ail.com" ], "favorite book" : "green eggs and ham", "location" : "shenzhen", "na
me" : "joe", "sex" : "male" }
3.3$addToSet和$each的组合使用
> db.users.update({"age":30},{"$addToSet":{"emails":{"$each":["[email protected]","joe
@python.org"]}}})
> db.users.find();
{ "_id" : ObjectId("4fc3a96f57bb647e0855d6ee"), "age" : 30, "emails" : [ "joe@gm
ail.com", "[email protected]", "[email protected]" ], "favorite book" : "green eggs and h
am", "location" : "shenzhen", "name" : "joe", "sex" : "male" }
3.4$pop从数组中删除元素
> db.lists.find();
{ "_id" : ObjectId("4fc4f2f04fa262c0188dbc5d"), "todo" : [ "dishes", "laundry",
"dry cleaning" ] }
> db.lists.update({"_id":ObjectId("4fc4f2f04fa262c0188dbc5d")},{"$pop":{"todo":-
1}})//-1表示从数组头开始删除,1表示从数组尾部开始删除
> db.lists.find()
{ "_id" : ObjectId("4fc4f2f04fa262c0188dbc5d"), "todo" : [ "laundry", "dry clean
ing" ] }
3.5$pull从数组中删除指定元素
> db.lists.update({},{"$pull":{"todo":"laundry"}})
> db.lists.find()
{ "_id" : ObjectId("4fc4f2f04fa262c0188dbc5d"), "todo" : [ "dry cleaning" ] }
3.6数组定位修改器
有2钟方法操作数组中的值：通过位置或者定位操作符（"$"）
3.7upsert选项
upsert是一种特殊的更新。要是没有文档符合更新条件，就会以这个条件和更新文档为基础创建一个新的文档。如果找到了匹配的文档，则正常更新.
> db.math.remove()
> db.math.find()
> db.math.update({"count":25},{"$inc":{"count":3}})
> db.math.find()
> db.math.update({"count":25},{"$inc":{"count":3}},true)
> db.math.find()
{ "_id" : ObjectId("4fc4fb5eb486ea65c4505ae0"), "count" : 28 }
3.8更新多个文档
db.math.update(query, object[, upsert_bool, multi_bool])
设置multi_bool为true即可
> db.runCommand({getLastError:1})
{ "n" : 0, "connectionId" : 1, "err" : null, "ok" : 1 }
上面代码可得到更新的记录数目
3.9返回更改记录
> db.runCommand({"findAndModify":"processes","query":{"status":"READY"},"sort":{
"priority":-1},"remove":true}).value
“findAndModify”：字符串，集合名
“query”：查询文档，用来检索文档的条件
"sort":排序结果的条件
“update”：修改器文档
“remove”:表示是否删除文档
“new”：表示返回的是更新前的文档还是更新后的文档