MongoDB 文档查询 I

文档查询

语法：

db.collectionName.find(query, projection);
//query ：可选，使用查询操作符指定查询条件
//projection：可选，使用投影操作符指定返回的键。
//默认省略，返回文档中所有键值。

//查询单条记录
db.collectionName.findOne(query, projection);

pretty() 方法可将结果格式化为可读模式

db.collectionName.find(query, projection).pretty();

query 条件

字段比较

操作	格式	示例	类比RDBMS
等于	{key:value}	{"CONTENT":"1"}	where CONTENT = '1'
小于	{key:{$lt:value}}	{"money":{$lt:50}}	where money < 50
小于或等于	{key:{$lte:value}}	{"money":{$lte:50}}	where money <= 50
大于	{key:{$gt:value}}	{"money":{$gt:50}}	where money > 50
大于或等于	{key:{$gte:value}}	{"money":{$gte:50}}	where money >= 50
不等于	{key:{$ne:value}}	{"money":{$ne:50}}	where money != 50
类型匹配	{key:{$type:value}}	{"money":{$type:1}}	--

AND 条件

格式：

{key1:value1, key2:value2}
//示例 db.demo.find({"AUTOR" : "houxx","CONTENT" : "1"}).pretty();

OR 条件

格式：

{$or: [{key1: value1}, {key2:value2}]}
//示例 
db.demo.find({$or: [{"CONTENT" : "1"}, {"CONTENT" : "2"}]},{_id:0}).pretty();

条件组合

直接把各个条件组合使用即可
示例：

//AUTOR 为 houxx ，且 money 的值等于1或大于2
db.demo.find({{"AUTOR":"houxx"},{$or: [{"money":1},{"money":{$gt:2}}]}},{_id:0}).pretty();

projection 条件

格式：

{字段名1:1,字段名2:1} // inclusion 模式，返回指定字段
{字段名1:0,字段名2:0} // exclusion 模式，指定字段不返回
//_id 键默认返回，需要主动指定 _id:0 才会隐藏
//两种模式不能混用，全 1 或全 0

$type 类型匹配

$type 取值

value	类型
1	Double
2	String
3	Object
4	Array
5	Binary data
6	Undefined（已废弃）
7	Object id
8	Boolean
9	Date
10	Null
11	Regular Expression
13	JavaScript
14	Symbol
15	JavaScript (with scope)
16	32-bit integer
17	Timestamp
18	64-bit integer
255	Min key（写作 -1）
127	Max key

示例：

//插入测试数据
> db.demo.insertMany([{"CONTENT":"1","AUTOR":"houxx"},{"CONTENT":"2","AUTOR":"houxx"},{"CONTENT":"1","AUTOR":"houxx"},{},{"CONTENT":"3","AUTOR":"houxx"}]);
{
        "acknowledged" : true,
        "insertedIds" : [
                ObjectId("5b26327f2afff603f6bd2ca5"),
                ObjectId("5b26327f2afff603f6bd2ca6"),
                ObjectId("5b26327f2afff603f6bd2ca7"),
                ObjectId("5b26327f2afff603f6bd2ca8"),
                ObjectId("5b26327f2afff603f6bd2ca9")
        ]
}
//直接查找所有
> db.demo.find();
{ "_id" : ObjectId("5b26327f2afff603f6bd2ca5"), "CONTENT" : "1", "AUTOR" : "houxx" }
{ "_id" : ObjectId("5b26327f2afff603f6bd2ca6"), "CONTENT" : "2", "AUTOR" : "houxx" }
{ "_id" : ObjectId("5b26327f2afff603f6bd2ca7"), "CONTENT" : "1", "AUTOR" : "houxx" }
{ "_id" : ObjectId("5b26327f2afff603f6bd2ca8") }
{ "_id" : ObjectId("5b26327f2afff603f6bd2ca9"), "CONTENT" : "3", "AUTOR" : "houxx" }
//查找所有格式化输出
> db.demo.find().pretty();
{
        "_id" : ObjectId("5b26327f2afff603f6bd2ca5"),
        "CONTENT" : "1",
        "AUTOR" : "houxx"
}
{
        "_id" : ObjectId("5b26327f2afff603f6bd2ca6"),
        "CONTENT" : "2",
        "AUTOR" : "houxx"
}
{
        "_id" : ObjectId("5b26327f2afff603f6bd2ca7"),
        "CONTENT" : "1",
        "AUTOR" : "houxx"
}
{ "_id" : ObjectId("5b26327f2afff603f6bd2ca8") }
{
        "_id" : ObjectId("5b26327f2afff603f6bd2ca9"),
        "CONTENT" : "3",
        "AUTOR" : "houxx"
}
//指定 _id 不返回
> db.demo.find({},{_id:0});
{ "CONTENT" : "1", "AUTOR" : "houxx" }
{ "CONTENT" : "2", "AUTOR" : "houxx" }
{ "CONTENT" : "1", "AUTOR" : "houxx" }
{  }
{ "CONTENT" : "3", "AUTOR" : "houxx" }
// AND 条件示例
> db.demo.find({"AUTOR" : "houxx","CONTENT" : "1"}).pretty();
{
        "_id" : ObjectId("5b26327f2afff603f6bd2ca5"),
        "CONTENT" : "1",
        "AUTOR" : "houxx"
}
{
        "_id" : ObjectId("5b26327f2afff603f6bd2ca7"),
        "CONTENT" : "1",
        "AUTOR" : "houxx"
}

// OR 条件示例
> db.demo.find({$or: [{"CONTENT" : "1"}, {"CONTENT" : "2"}]},{_id:0}).pretty();
{ "CONTENT" : "1", "AUTOR" : "houxx" }
{ "CONTENT" : "2", "AUTOR" : "houxx" }
{ "CONTENT" : "1", "AUTOR" : "houxx" }