MongoDB常用语句
- 使用
- 创建和删除
- 查询
- 条件查询
- 模糊查询
- 分页
- 排序
- 聚合
- 两表连接
- 插入
使用
展示数据库
show dbs 或 show databases
查看当前在使用的数据库
db
展示数据库下所有表
show collections 或 show tables;
终端内容过多，用该指令清屏
cls
创建和删除
如果数据库【school】不存在，则创建它，否则就切换到【school】数据库。
因为是创建了一个空的，所以它只存放在内存中，没到磁盘里。用show dbs无法查看，但db可以
use school
删除当前使用的数据库
db.dropDatabase() <=> drop database school;
创建名为student的集合（用创建语句，插入内容为空也可以创建）
db.createCollection("student")
db.student.insertOne({})
删除student集合
db.student.drop() <=> drop table student;
查询
db.student.find().pretty() 美化输出结果
查询所有记录
db.student.find() <=> select * from student;
查询指定列 name、age 数据
当然 name 也可以用 true 或 false,当用 ture 的情况下和 name:1 效果一样，如果用 false 就是排除 name，显示 name 以外的列信息。
db.student.find({}, {name: 1, age: 1}); <=> select name, age from student;
查询去重后的一列
db.student.distinct("name") <=> select distict name from student;
条件查询
db.student.find({"age": 22}) <=> select * from student where age = 22;
db.student.find({age: {$gt: 22}}) <=> select * from student where age > 22;
db.student.find({age: {$lt: 22}}) <=> select * from student where age < 22;
db.student.find({age: {$gte: 25}}) <=> select * from student where age >= 25;
db.student.find({age: {$lte: 25}}) <=> select * from student where age <= 25;
db.student.find({age: {$ne: 25}}) <=> select * from student where age != 25;
db.student.find({age: {$gte: 23, $lte: 25}}); <=> select * from student where age>=23 and age <= 25;
db.student.find({name: 'zhangsan', age: 22}); <=> select * from student where name = 'zhangsan' and age = 22;
db.student.find({$or: [{age: 22}, {age: 25}]}); <=> select * from student where age = 22 or age = 25;
db.student.find({age :{$in:[22,25]}}); <=> select * from student where age in (22,25);
db.student.find({createtime:{$gt:isodate("2020-11-09t00:00:00z")}}); <=> select * from student where createtime> '2020-11-09 00:00:00'; db.student.aggregate({$match:{createtime:{$gte:isodate("2020-11-10t00:00:00z"),$lt:isodate("2020-11-11t00:00:00z")}}}); <=> select * from student where createtime >= '2020-11-10 00:00:00' and createtime < '2020-11-11 00:00:00';
查询指定列
db.student.find({age: {$gt: 25}}, {name: 1, age: 1}); <=> select name, age from student where age > 25;
模糊查询
db.student.find({name: /zhang/}) <=> select * from student where name like '%zhang%';
db.student.find({name: /^zhang/}) <=> select * from student where name like 'zhang%';
db.student.find({name: /zhang$/}) <=> select * from student where name like '%zhang';
分页
# 查询前 5 条数据
db.student.find().limit(5); <=> select * from student limit 5;
# 查询在 6-10条 之间的数据
db.student.find().limit(10).skip(5); <=> select * from student limit 5,5;
查询 10 条以后的数据
db.userInfo.find().skip(10);
排序
# 升序
db.student.find().sort({age: 1}); <=> select * from student order by age asc;
# 降序
db.student.find().sort({age: -1}); <=> select * from student order by age desc;
聚合
db.student.find({age: {$gte: 25}}).count(); <=> select count(*) from student where age >= 20;db.student.aggregate({$group:{_id:null,score:{$sum:"$score"}}}); <=> select sum(score) from student;db.student.aggregate({$group:{_id:null,score:{$avg:"$score"}}}); <=> select avg(score) from student;db.student.aggregate({$match:{createtime:{$gte:isodate("2020-11-10t00:00:00z"),$lt:isodate("2020-11-11t00:00:00z")}}},{$group:{_id:null,score:{$sum:"$score"}}}); <=> select sum(score) from student where createtime >= '2020-11-10 00:00:00' and createtime < '2020-11-11 00:00:00';
两表连接
【student】表和【stuAdress】表关联，两表关联字段是userId相等，关联条件是userId等于2102123
db.student.aggregate([{$lookup:{from: "stuAdress",localField: "userId",foreignField: "userId",as: "address_detail"}},{ $match : {"userId" :"2102123"} }
])
有点相当于 select a.*，b.* from student a, stuAdress b where a.userId=b.userId and userId='2102123'
输出结果长这样
[{_id: 1,userId: '2102123',username: 'zhangsan',age:'32',address_docs: [{_id: 1,userId: '2102123',address: '黑龙江哈尔滨'},{_id: 3,userId: '2102123',address: '四川成都'}]}
]
skip(), limilt(), sort()三个放在一起执行的时候，执行的顺序是先 sort(), 然后是 skip()，最后是显示的 limit()。
插入
# 新建一个实例，再插入
doc={"name":"zhangsan","age":"32","sex":"man"}
db.test.insertOne(doc)
# 数据内容直接写入语句
db.test.insertOne({"name":"zhangsan","age":"32","sex":"man"})
# 插入数据成功会返回true，而且会在数据中添加一个_id属性
db.test.insertOne({"name":"zhangsan","age":"32","sex":"man"}) （将数据插入到test表中）
db.coil_new_test.insertOne({"name":"zhangsan","age":"32","sex":"man"}) （将数据插入到coil_new_test表中）
db.coil.new.test.insertOne({"name":"zhangsan","age":"32","sex":"man"}) （将数据插入到coil.new.test表中）
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