重新学习mongodb:构建查询

布满荆棘的人生 2022-05-10 15:42 264阅读 0赞

**findone和find:**

find返回一个光标。findone返回一个文件；

**忽略、限制和排序查询选项：**

db.reviews.find().skip().limit(12);

**加入排序功能：**

db.reviews.find().sort(\{'\_helpful\_votes':-1\}).limit(12)

![70][]

**不返回整个文件，使用投影返回限制字段：**

db.users.findOne(\{username: 'kbanker',  
  hashed\_password: 'bd1cfa194c3a603e7186780824b04419'\},  
  \{\_id: 1\})

所有：

// Product page
    db.products.findOne({'_id': ObjectId("4c4b1476238d3b4dd5003981")})
    
    // Displaying a product page.
    //<start id="product-page"/>  
    product  = db.products.findOne({'slug': 'wheel-barrow-9092'})
    category = db.categories.findOne({'_id': product['main_cat_id']})
    reviews  = db.reviews.find({'product_id': product['_id']})
    //<end id="product-page"/>  
    
    //<start id="product-page-find-one"/>  
    db.products.find({'slug': 'wheel-barrow-9092'}).limit(1)
    //<end id="product-page-find-one"/>  
    
    //<start id="product-page-review-skip-limit"/>  
    reviews = db.reviews.find({'product_id': product['_id']}).skip(0).limit(12)
    //<end id="product-page-review-skip-limit"/>  
    
    //<start id="product-page-review-skip-limit-sort"/>  
    reviews = db.reviews.find({'product_id': product['_id']}).
                               skip(0).limit(12).sort({helpful_votes: -1})
    //<end id="product-page-review-skip-limit-sort"/>  
    
    
    //<start id="product-page-final"/>  
    var page_number = 10
    product  = db.products.findOne({'slug': 'wheel-barrow-9092'})
    category = db.categories.findOne({'_id': product['main_cat_id']})
    reviews_count = db.reviews.count({'product_id': product['_id']})
    reviews = db.reviews.find({'product_id': product['_id']}).
                             skip((page_number - 1) * 12).
                             limit(12).
                             sort({'helpful_votes': -1})
    //<end id="product-page-final"/>  
    
    //<start id="product-listing-page"/>  
    category = db.categories.findOne({'slug': 'outdoors'})
    siblings = db.categories.find({'parent_id': category['_id']})
    products = db.products.find({'category_id': category['_id']}).
                               skip((page_number - 1) * 12).
                               limit(12).
                               sort({helpful_votes: -1})
    //<end id="product-listing-page"/>  
    
    // Displaying the category hierarchy
    //<start id="category-page-root"/>  
    categories = db.categories.find({'parent_id': null})
    //<end id="category-page-root"/>

**mongodb支持使用正则表达式查询：**

db.users.find(\{'last\_name':/^Ba/\});

**查询特定的范围：**

db.users.find(\{'addresses.zip':\{'$gt':10019,'$lt':10040\}\})

db.users.findOne({username: 'kbanker',
      hashed_password: 'bd1cfa194c3a603e7186780824b04419'})
    
    db.users.findOne({username: 'kbanker',
      hashed_password: 'bd1cfa194c3a603e7186780824b04419'},
      {_id: 1})
    
    db.users.find({last_name: 'Banker'})
    
    db.users.find({last_name: /^Ba/})
    
    db.users.find({'addresses.zip': {$gte: 10019, $lt: 10040}})
    
    db.orders.find({'line_items.sku': "9092"}) 
    
    db.orders.find({'line_items.sku': "9092",
        'purchase_date': {$gte: new Date(2009, 1, 1)}})
    
    db.orders.ensureIndex({'line_items.sku': 1, 'purchase_date': 1})
    
    user_ids = db.orders.find({'line_items.sku': "9092",
      purchase_date: {'$gt': new Date(2009, 0, 1)}},
      {user_id: 1, _id: 0})
    users = db.users.find({_id: {$in: user_ids}})

**查询选择：**

![70 1][]

**设置运算**

![70 2][]

**布尔运算符：**

![70 3][]

查找关键字文档：

db.products.find({'details.color':{$exists:false}})//没有这个字段的数据

![70 4][]

匹配子文档

![70 5][]

关键字的顺序非常重要。

数组：

![70 6][]

JavaScript查询运算符：

![70 7][]

正则表达式：

![70 8][]

![70 9][]

查询选择：

映射：

![70 10][]

![70 11][]

跳过和限制：

skip , limit

[70]: /images/20220505/4ded67087dd447d789e967a92fa23e54.png
[70 1]: /images/20220505/77840d3f561e43079ce07e9f975e0610.png
[70 2]: /images/20220505/c644d40d6aac490b8d2567eaae5a4429.png
[70 3]: /images/20220505/bad7bab244b04d6ba1ce2824d08fd43b.png
[70 4]: /images/20220505/23254192416d494ba9b48a9138888931.png
[70 5]: /images/20220505/62b6a5c352884322a35998eea91a86eb.png
[70 6]: /images/20220505/230e7ae0b1044e41827406b5f251e756.png
[70 7]: /images/20220505/f61cc737813d4c53ac9caf37b809d3e7.png
[70 8]: /images/20220505/6233b60690fb4106a84f139207782a79.png
[70 9]: /images/20220505/06237c9f778d42098817a96fc38b8e96.png
[70 10]: /images/20220505/8e19572a687248e4ad9c77bffad21525.png
[70 11]: /images/20220505/09ca98b1012944eea9fec4fab8706fc6.png