mongodb 高级查询 group count 查询

最新推荐文章于 2023-12-14 21:42:24 发布

lgh1117

最新推荐文章于 2023-12-14 21:42:24 发布

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分类专栏： mongodb 文章标签： mongodb query function string

本文链接：https://blog.youkuaiyun.com/lgh1117/article/details/7318812

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本文介绍了MongoDB中使用的基本查询操作符，如$gt、$lt等，并演示了如何组合这些操作符进行复杂查询，同时还包括排序、计数及分组等功能的使用方法。

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条件操作符
$gt : >
$lt : <
$gte: >=
$lte: <=
$ne : !=、<>
$in : in
$nin: not in
$all: all
$not: 反匹配(1.3.3及以上版本)

以下都是引用此集合

DBCollection coll = db.getCollection("employees");

查询 name <> "li" and age >= 18的数据

BasicDBObject query = new BasicDBObject();
query.put("name", new BasicDBObject().append("$ne", "liguohui"));
query.put("age", new BasicDBObject().append("$gte", 18));
coll.find(query)

查询 age> 10 and age<= 30的数据

BasicDBObject query = new BasicDBObject();
query.put("age", new BasicDBObject().append("$gt", 10));
query.put("age", new BasicDBObject().append("$lte", 30));

coll.find(query);

查询 age in (20,22,24)的数据

BasicDBObject query = new BasicDBObject();
BasicDBList values = new BasicDBList();  
values.add(20);  
values.add(22); 
values.add(24);
query.put("age", new BasicDBObject("$in", values));  
DBCursor cur = coll.find(query);

查询 age取模10等于0的数据

BasicDBObject query = new BasicDBObject();
BasicDBList values = new BasicDBList();  
values.add(10);  
values.add(0); 
query.put("age", new BasicDBObject("$mod", values));  
DBCursor cur = coll.find(query);

查询不匹配name=B*带头的记录

BasicDBObject query = new BasicDBObject();
Pattern p = Pattern.compile("^B.*$");
query.put("name",p);
DBCursor cur = coll.find(query);

排序sort()
以年龄升序asc

DBCursor cur = coll.find().sort(new BasicDBObject().append("name", 1));

以年龄降序desc

DBCursor cur = coll.find().sort(new BasicDBObject().append("name", -1));

查询记录条数count()

long count = coll.getCount();

BasicDBObject query = new BasicDBObject();
query.put("age", new BasicDBObject("$lge", 10));  
long count = coll.getCount(query);

分组group()

BasicDBObject key = new BasicDBObject(); 
key.put("name", "true"); 
BasicDBObject initial = new BasicDBObject(); 
initial.put("age", 0); 
BasicDBObject condition = new BasicDBObject(); 
// condition.put("name", "liguohui"); 
String reduceString = "function(obj,prev) { prev.age += obj.age; }"; 
DBObject dbo = coll.group(key, condition , initial, reduceString); 
System.out.println(dbo);

分组group() and count()

BasicDBObject key = new BasicDBObject(); 
key.put("name", "true"); 
BasicDBObject initial = new BasicDBObject(); 
initial.put("count", 0); 
BasicDBObject condition = new BasicDBObject(); 
// condition.put("name", "liguohui"); 
String reduceString = "function(obj,prev) { prev.count++; }"; 
DBObject dbo = coll.group(key, condition , initial, reduceString); 
System.out.println(dbo);