MySQL与MongoDB语法对比（简单）

在实习的过程中，主要是对mongo中的数据进行select操作，故重点总结的是mongo的查询语法。

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-- 增
insert into student(name,sex,age) values('gx','female','20');
db.getCollection('student').save({"name":"gx","sex":"female","age":22});
var stuinfo={"name":"gx","sex":"女","age":22}
db.getCollection('student').insert(stuinfo);

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-- 删
delete from student where name="gx";
db.getCollection("student").remove("name":"gx");

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-- 改
update student set age="18" where name="gx";
db.getCollection("student").update({"name":"gx"},{$set:{"age":18}});
db.getCollection("student").update({"name":"gx"},{"age":18});
update student set age=age+1;
db.getCollection("student").update({},{$inc:{"age":1}});

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-- 查
-- 1. 查询全部列
select * from student;
db.getCollection("student").find();
db.getCollection("student").find({});
-- 2. 查询不重复的列
select distinct name from student;
db.getCollection("student").find({});
-- 3.条件查询（可从条件的反面查询）
-- 等于
select * from student where age=20;
db.getcollection('student').find({"age":20});
-- 特殊的等于
select * from student where a=b;
db.getCollection('student').find({$where:"this.a== this.b"});
db.getCollection('student').find({$where:function() {return this.a==this.b}});
-- 不等于
select * from student where age<>20;
db.getcollection('student').find({"age":{$ne:20}});
db.getCollection('student').find({$nor:[{"age":20}]});
-- 大于
select * from student where age>20;
db.getCollection('student').find({"age":{$gt:20}});
-- 小于
select * from student where age<20 ;
db.getCollection('student').find({"age":{$lt:20}});
-- 大于等于
select * from student where age>=20;
db.getCollection('student').find({"age":{$gte:20}};
db.getCollection('student').find({age:{$not:{$lt:20}}});
-- 小于等于
select * from student where age<=20;
db.getCollection('student').find({"age":{$lte:20}});
db.getCollection('student').find({"age":{$not:{$gt:20}}});
-- 4.AND运算符
-- 数值范围查询
select * from student where age between 15 and 20;
db.getcollection('student').find({age:{$gt:15,$lt:20}});
-- 多条件查询，and连接
select * from sudent where age=20 and sex="女";
db.getcollection('student').find({"age":20,"sex":"女"});
db.getCollection('student').find({$and:[{"age":20},{"sex":"女"}]});
-- 5. OR运算符
select * from student where age=20 or sex="女";
db.getCollection('student').find({$or:[{"age":20},{"sex":"女"}]});
-- 6.空值查询
-- 注意：不加exists将会把字段不存在的记录也查询出来
select * fron student where name is null;
db.getCollection('student').find({name:{$in:[null],$exists:true}});
-- 7. IN/ NOT IN
-- IN
select * from student where name in ('name1','name2');
db.getCollection('student').find({name:{$in:['name1','name2']}});
-- NOT IN
select * from student where name not in ('name1','name2');
db.getCollection('student').find({name:{$nin:['name1','name2']}});
-- 8. COUNT计数
select count(*) from student;
db.getCollection('student').find().count();
select count(name) from student;
db.getCollection('student').find({"name":{$exists:true}}).count();
-- 9.模糊匹配查询(正则表达式)
select * from student where name like "%g%";
db.getCollection('student').find({"name":/g/})
select * from student where name like "g%";
db.getCollection('student').find({"name":/^g/});
-- 10.排序
-- 升序
select * from student order by age asc;
db.getCollection('student').find().sort({"age":1});
-- 降序
select * from student order by age desc;
db.getCollection('student').find().sort({"age":-1});
--11.查询某几行
select top 10 from student;
db.getCollection('student').find().limit(10);
--12.查询指定的列
select name,sex from student;
db.getcollection('student').find({},{"name":1,"sex":1,"_id":0});
select name,sex from student where sex="女"
-- 13.查询内嵌文档
db.getCollection("backend_charts").find({area:{x:278,y:432,w:71,h:114}});
db.getCollection("backend_charts").find
({"area.x":278,"area.y":432,"area.w":71,"area.h":114});