mongodb的基本语法（二）

一、聚集集合查询

1、查询所有记录

db.userInfo.find();

相当于：select* from userInfo;

默认每页显示20条记录，当显示不下的情况下，可以用it迭代命令查询下一页数据。注意：键入it命令不能带“；”

但是你可以设置每页显示数据的大小，用DBQuery.shellBatchSize= 50;这样每页就显示50条记录了。

2、查询去掉后的当前聚集集合中的某列的重复数据

db.userInfo.distinct("name");

会过滤掉name中的相同数据

相当于：select distict name from userInfo;

3、查询age = 22的记录

db.userInfo.find({"age": 22});

相当于： select * from userInfo where age = 22;

4、查询age > 22的记录

db.userInfo.find({age: {$gt: 22}});

相当于：select * from userInfo where age >22;

5、查询age < 22的记录

db.userInfo.find({age: {$lt: 22}});

相当于：select * from userInfo where age <22;

6、查询age >= 25的记录

db.userInfo.find({age: {$gte: 25}});

相当于：select * from userInfo where age >= 25;

7、查询age <= 25的记录

db.userInfo.find({age: {$lte: 25}});

8、查询age >= 23 并且 age <= 26

db.userInfo.find({age: {$gte: 23, $lte: 26}});

9、查询name中包含 mongo的数据

db.userInfo.find({name: /mongo/});

//相当于%%

select * from userInfo where name like ‘%mongo%';

10、查询name中以mongo开头的

db.userInfo.find({name: /^mongo/});

select * from userInfo where name like ‘mongo%';

11、查询指定列name、age数据

db.userInfo.find({}, {name: 1, age: 1});

相当于：select name, age from userInfo;

当然name也可以用true或false,当用ture的情况下河name:1效果一样，如果用false就是排除name，显示name以外的列信息。

12、查询指定列name、age数据, age > 25

db.userInfo.find({age: {$gt: 25}}, {name: 1, age: 1});

相当于：select name, age from userInfo where age >25;

13、按照年龄排序

升序：db.userInfo.find().sort({age: 1});

降序：db.userInfo.find().sort({age: -1});

14、查询name = zhangsan, age = 22的数据

db.userInfo.find({name: 'zhangsan', age: 22});

相当于：select * from userInfo where name = ‘zhangsan' and age = ‘22';

15、查询前5条数据

db.userInfo.find().limit(5);

相当于：selecttop 5 * from userInfo;

16、查询10条以后的数据

db.userInfo.find().skip(10);

相当于：select * from userInfo where id not in (

select top 10 * from userInfo

);

17、查询在5-10之间的数据

db.userInfo.find().limit(10).skip(5);

可用于分页，limit是pageSize，skip是第几页*pageSize

18、or与查询

db.userInfo.find({$or: [{age: 22}, {age: 25}]});

相当于：select * from userInfo where age = 22 or age = 25;

19、查询第一条数据

db.userInfo.findOne();

相当于：select top 1 * from userInfo;

db.userInfo.find().limit(1);

20、查询某个结果集的记录条数

db.userInfo.find({age: {$gte: 25}}).count();

相当于：select count(*) from userInfo where age >= 20;

21、按照某列进行排序

db.userInfo.find({sex: {$exists: true}}).count();

相当于：select count(sex) from userInfo;

二、语句块操作

1、简单Hello World

print("Hello World!");

这种写法调用了print函数，和直接写入"Hello World!"的效果是一样的；

2、将一个对象转换成json

tojson(new Object());

tojson(new Object('a'));

3、循环添加数据

 for (var i = 0; i < 30; i++) {

     db.users.save({name: "u_" + i, age: 22 + i, sex: i % 2});

 };

这样就循环添加了30条数据，同样也可以省略括号的写法

for (var i = 0; i < 30; i++) db.users.save({name: "u_" + i, age: 22 + i, sex: i % 2});

也是可以的，当你用db.users.find()查询的时候，显示多条数据而无法一页显示的情况下，可以用it查看下一页的信息；

4、find 游标查询

var cursor = db.users.find();

    while (cursor.hasNext()) {

        printjson(cursor.next());

}

这样就查询所有的users信息，同样可以这样写

var cursor = db.users.find();

    while (cursor.hasNext()) {

 printjson(cursor.next);

}

同样可以省略{}号

5、forEach迭代循环

db.users.find().forEach(printjson);

forEach中必须传递一个函数来处理每条迭代的数据信息

6、将find游标当数组处理

var cursor = db.users.find();

cursor[4];

取得下标索引为4的那条数据

既然可以当做数组处理，那么就可以获得它的长度：cursor.length();或者cursor.count();

那样我们也可以用循环显示数据

for (var i = 0, len = c.length(); i < len; i++) printjson(c[i]);

7、将find游标转换成数组

var arr = db.users.find().toArray();

printjson(arr[2]);

用toArray方法将其转换为数组

8、定制我们自己的查询结果

只显示age <= 28的并且只显示age这列数据

db.users.find({age: {$lte: 28}}, {age: 1}).forEach(printjson);

db.users.find({age: {$lte: 28}}, {age: true}).forEach(printjson);

排除age的列

db.users.find({age: {$lte: 28}}, {age: false}).forEach(printjson);

9、forEach传递函数显示信息

db.things.find({x:4}).forEach(function(x) {print(tojson(x));});

三、官方提供的操作语句对照表：

上行：SQL 操作语句

下行：Mongo 操作语句

CREATE TABLE USERS (a Number, b Number)

db.createCollection("mycoll") 

INSERT INTO USERS VALUES(1,1)

db.users.insert({a:1,b:1}) 

SELECT a,b FROM users

db.users.find({}, {a:1,b:1}) 

SELECT * FROM users

db.users.find() 

SELECT * FROM users WHERE age=33

db.users.find({age:33}) 

SELECT a,b FROM users WHERE age=33

db.users.find({age:33}, {a:1,b:1}) 

SELECT * FROM users WHERE age=33 ORDER BY name

db.users.find({age:33}).sort({name:1}) 

SELECT * FROM users WHERE age>33

db.users.find({'age':{$gt:33}})}) 

SELECT * FROM users WHERE age<33

db.users.find({'age':{$lt:33}})}) 

SELECT * FROM users WHERE name LIKE "%Joe%"

db.users.find({name:/Joe/}) 

SELECT * FROM users WHERE name LIKE "Joe%"

db.users.find({name:/^Joe/}) 

SELECT * FROM users WHERE age>33 AND age<=40

db.users.find({'age':{$gt:33,$lte:40}})}) 

SELECT * FROM users ORDER BY name DESC

db.users.find().sort({name:-1}) 

SELECT * FROM users WHERE a=1 and b='q'

db.users.find({a:1,b:'q'}) 

SELECT * FROM users LIMIT 10 SKIP 20

db.users.find().limit(10).skip(20) 

SELECT * FROM users WHERE a=1 or b=2

db.users.find( { $or : [ { a : 1 } , { b : 2 } ] } ) 

SELECT * FROM users LIMIT 1

db.users.findOne() 

SELECT DISTINCT last_name FROM users

db.users.distinct('last_name') 

SELECT COUNT(*y) FROM users

db.users.count() 

SELECT COUNT(*y) FROM users where AGE > 30

db.users.find({age: {'$gt': 30}}).count() 

SELECT COUNT(AGE) from users

db.users.find({age: {'$exists': true}}).count() 

CREATE INDEX myindexname ON users(name)

db.users.ensureIndex({name:1}) 

CREATE INDEX myindexname ON users(name,ts DESC)

db.users.ensureIndex({name:1,ts:-1}) 

EXPLAIN SELECT * FROM users WHERE z=3

db.users.find({z:3}).explain() 

UPDATE users SET a=1 WHERE b='q'

db.users.update({b:'q'}, {$set:{a:1}}, false, true) 

UPDATE users SET a=a+2 WHERE b='q'

db.users.update({b:'q'}, {$inc:{a:2}}, false, true) 

DELETE FROM users WHERE z="abc"

db.users.remove({z:'abc'});

整理自脚本之家