nodejs mongodb 查询要看的文章

hcwzwx

　　http://www.iyunv.com/refactor/archive/2012/07/30/2591344.html
　　数组很大多数情况下可以这样理解:每一个元素都是整个键的值.
　　db.users.findOne({"userName":"wyx","emails":"bbb@qq.com"})能匹配到
　　{
　　userName: 'wyx',
　　emails:[
　　'aaa@qq.com',
　　'bbb@qq.com',
　　'ccc@qq.com'
　　]
　　}
　　

MongoDB高级查询
　　http://www.nonb.cn/blog/mongodb-advanced-queries.html

Node+Mongoose常用查询中文文档
　　http://www.nonb.cn/blog/nodejs-mongoose-query-chinaese.html
　　
　　推荐看这三篇 mongodb的查询，以及nodejs和mongoose联用的情况
　　看完mongoose的基本查询就没问题了
　　
　　如何在mongodb中使用索引？
　　http://www.iyunv.com/huangxincheng/archive/2012/02/29/2372699.html
　　

MongoDB组合索引的优化
　　非常好的文章，将索引，排序等问题的性能优劣取舍讲的很透彻
　　http://www.iyunv.com/article/2012-11-09/2811690-optimizing-mongodb-compound
　　explain方法若出现BasicCursor可以视为警告，它意味着MongoDB将对数据集做一个完全的扫描。当数据集里包含上千万条信息时，这完全是行不通的。因此要考虑加上适当的索引
　　
　　
　　常用的关键字， count, distinct, group ....
　　http://www.iyunv.com/huangxincheng/archive/2012/02/21/2361205.html
　　
　　
　　
　　mongoose中的2中操作方法，
　　callback and query returned
　　http://mongoosejs.com/docs/queries.html

Queries
　　Documents can be retrieved through several static helper methods of models.
　　Any model method which involves specifying query conditions can be executed two ways:
　　When a callback function:

• is passed, the operation will be executed immediately with the results passed to the callback.
  
• is not passed, an instance of Query is returned, which provides a special QueryBuilder interface for you.
  

　　Let's take a look at what happens when passing a callback:

var Person = mongoose.model('Person', yourSchema); // Query
// find each person with a last name matching 'Ghost', selecting the `name` and `occupation` fields
Person.findOne({ 'name.last': 'Ghost' }, 'name occupation', function (err, person) {
if (err) return handleError(err);
console.log('%s %s is a %s.', person.name.first, person.name.last, person.occupation) // Space Ghost is a talk show host.
})
　　Here we see that the query was executed immediately and the results passed to our callback. All callbacks in Mongoose use the pattern: callback(error, result). If an error occurs executing the query, the errorparameter will contain an error document, and result will be null. If the query is successful, the errorparameter will be null, and the result will be populated with the results of the query.


　　Anywhere a callback is passed to a function in Mongoose, the callback follows the patterncallback(error, results).
　　Now let's look at what happens when no callback is passed:

// find each person with a last name matching 'Ghost'
var query = Person.findOne({ 'name.last': 'Ghost' });
// selecting the `name` and `occupation` fields
query.select('name occupation');
// execute the query at a later time
query.exec(function (err, person) {
if (err) return handleError(err);
console.log('%s %s is a %s.', person.name.first, person.name.last, person.occupation) // Space Ghost is a talk show host.
})
　　An instance of Query was returned which allows us to build up our query. Taking this example further:

Person
.find({ occupation: /host/ })
.where('name.last').equals('Ghost')
.where('age').gt(17).lt(66)
.where('likes').in(['vaporizing', 'talking'])
.limit(10)
.sort('-occupation')
.select('name occupation')
.exec(callback);