mongodb(三):一些修改器和定位器
1. 准备数据> db.blog.posts.insert(
... {
... "title":"A blogpost",
... "content":"..."
... }
... )
> show collections
blog.posts
foo
system.indexes
2. 添加一个评论comments,评论中有名字，email,content可以看作一个集合体，用数组表示，用数组修改器"$push”,它会向数组末尾加入一个元素，如果数组不存在，则会创建这个数组
> db.blog.posts.update(
... {
... "title":"A blogpost"
... }
... ,
... {
... "$push":
... {
... "comments":
... {
... "name":"bob",
... "email":"bob@example.com",
... "content":"goodpost."
... }
... }
... }
... )
> db.blog.posts.find().pretty()
{
"_id" :ObjectId("53f74fda78a0a91d1242f0ed"),
"comments" : [
{
"name" : "bob",
"email" :"bob@example.com",
"content" : "goodpost."
}
],
"content" : "...",
"title" : "A blogpost"
}
3. “$ne”和"$addToSet”,如果一个值不在数组里面，则加进去
> db.users.insert(
... {
... "username":"joe",
... "emails":[
... "joe@example.com",
... "joe@gmail.com",
... "joe@yahoo.com"
... ]
... }
... ) “$ne”先判断是否存在，插入的时候要借助”$push” > db.users.update(
... {"_id" :ObjectId("53f75dd678a0a91d1242f0ef"),"emails":{"$ne":"joe@example.com"}}, ...{"$push":{"emails":"joe@example.com"}}
... )
> db.users.find().pretty()
{
"_id" :ObjectId("53f75dd678a0a91d1242f0ef"),
"username" : "joe",
"emails" : [
"joe@example.com",
"joe@gmail.com",
"joe@yahoo.com"
]
} “$addToSet”,先判断，插入的时候不需要借助”$push” > db.users.update(
... {"_id" :ObjectId("53f75dd678a0a91d1242f0ef")},
...{"$addToSet":{"emails":"joe@163.com"}}
... )
> db.users.find().pretty()
{
"_id" :ObjectId("53f75dd678a0a91d1242f0ef"),
"emails" : [
"joe@example.com",
"joe@gmail.com",
"joe@yahoo.com",
"joe@163.com"
],
"username" : "joe"
}
4. “$addToSet”和”$each”组合起来，可以添加多个值
> db.users.update(
... {"_id" :ObjectId("53f7645b78a0a91d1242f0f0")},
... {"$addToSet":
...{"emails":{"$each":["joe@php.net","joe@qq.com","joe@hostmail.com"]}}
... }
... )
> db.users.find().pretty()
{
"_id" :ObjectId("53f7645b78a0a91d1242f0f0"),
"emails" : [
"joe@example.com",
"joe@gmail.com",
"joe@yahoo.com",
"joe@163.com",
"joe@hostmail.com",
"joe@php.net",
"joe@qq.com"
],
"username" : "joe"
}
5. “$pop”删除数组的任何一端
删除尾端：
> db.users.update(
... {"_id" :ObjectId("53f7645b78a0a91d1242f0f0")},
...{"$pop":{"emails":1}}
... )
> db.users.find().pretty()
{
"_id" : ObjectId("53f7645b78a0a91d1242f0f0"),
"emails" : [
"joe@example.com",
"joe@gmail.com",
"joe@yahoo.com",
"joe@163.com",
"joe@hostmail.com",
"joe@php.net"
],
"username" : "joe"
} 删除头： > db.users.update(
... {"_id" :ObjectId("53f7645b78a0a91d1242f0f0")},
...{"$pop":{"emails":-1}}
... )
> db.users.find().pretty()
{
"_id" :ObjectId("53f7645b78a0a91d1242f0f0"),
"emails" : [
"joe@gmail.com",
"joe@yahoo.com",
"joe@163.com",
"joe@hostmail.com",
"joe@php.net"
],
"username" : "joe"
}
6. “$pull”根据特定的条件删除
> db.users.update(
... {"_id" :ObjectId("53f7645b78a0a91d1242f0f0")},
...{"$pull":{"emails":"joe@php.net"}}
... )
> db.users.find().pretty()
{
"_id" :ObjectId("53f7645b78a0a91d1242f0f0"),
"emails" : [
"joe@gmail.com",
"joe@yahoo.com",
"joe@163.com",
"joe@hostmail.com"
],
"username" : "joe"
}
7. 数组定位修改器”$”
>db.blog.posts.find().pretty()
{
"_id": ObjectId("53f7771678a0a91d1242f0f1"),
"comments": [
{
"name": "bob",
"email": "bob@example.com",
"content": "good post."
}
],
"content": "...",
"title": "A blog post"
}
>
> db.blog.posts.update(
... {"comments.content": "good post."},
...{"$set":{"comments.$.content":"bad post."}}
... )
> db.blog.posts.find().pretty()
{
"_id": ObjectId("53f7771678a0a91d1242f0f1"),
"comments": [
{
"content": "bad post.",
"email": "bob@example.com",
"name": "bob"
}
],
"content": "...",
"title": "A blog post"
}
注明：使用”$”的时候第一个参数和"comments.$.content"指向同一种属性 否则会抱错：can't append to array using string field name[$]
用数组下标，不需要 第一个参数和第二个参数的键要匹配 > db.blog.posts.update(
... {"_id" :ObjectId("53f7771678a0a91d1242f0f1")},
...{"$set":{"comments.0.content":"good post."}}
... )
> db.blog.posts.find().pretty()
{
"_id" :ObjectId("53f7771678a0a91d1242f0f1"),
"comments" : [
{
"content" : "goodpost.",
"email" :"bob@example.com",
"name" : "bob"
}
],
"content" : "...",
"title" : "A blogpost"
}
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