mongdb--3. Query operations

1. Preparatory work

(1) Start MONGO

Enter the bin/directory of the MONGO installation directory,./mongod

(2) Start MONGO client

./mongo

(3) View all libraries

Show DBS;

(4) Switch to LVYF Library

Use LVYF

(5) View all collections

Show collections;

(6) Check data from a collection

Db.first_col.find ();

2. Enquiry

(1) View all, pretty () function is to format the JSON data

Db.collection_name.find (). pretty ();

>"_id": ObjectId ("575e879380d09b176a58ce64"), "name": "Lvyafei", "age": +, "sex": "M", "Address": "http: www.lvyf.com "_id": ObjectId ("575e880980d09b176a58ce65"), "name": "Chenjl", "Age": $, "Sex": "W", "address ":" http://www.chenjl.com "" _id ": ObjectId (" 575e889880d09b176a58ce66 ")," name ":" Child "," Age ": 2," Sex ":" M " , "Address": "Http://www.child.com", "status": "Cry and Laugh"}

(2) Conditional query

Operation	Format	Example	The corresponding SQL statement
Equals	{Key:value}	{NAME:LVYF}	where Name= ' Lvyf '
Less than	{key: {&lt:value}}	{age: {&lt:20}}	Where Age < 20
Less than or equal to	{key: {&lte:value}}	{age: {&lte:20}}	where Age <=20
Greater than	{key: {&gt:value}}	{age: {&gt:3}}	Where Age > 3
Greater than or equal to	{key: {&gte:vlaue}}	{age: {&gte:3}}	where Age >=3
Not equal to	{key: {&ne:value}}	{name: {&NE:LVYF}}	WHERE name! = ' LVYF '

(3) and conditions

Query records based on gender and name, corresponding SQL statement where name= ' Lvyafei ' and sex = ' M '

Db.first_col.find ({name: "Lvyafei", Sex: "M"}). Pretty (){    "_id": ObjectId (" 575e879380d09b176a58ce64 "),    " name ":" Lvyafei ",    " age ": +,    " sex ":" M " ,    " Address ":" Http://www.lvyf.com "}

(4) or condition, grammar

Db.collection_name.find ({$or: [{key1:value1}, {key2:value2}]  });

Search examples by name or gender:

>db.first_col.find ({$or: [{name: ' Lvyafei '},{sex: ' M '}]})' _id ': ObjectId ("  575e879380d09b176a58ce64 ")," name ":" Lvyafei "," age ": +," sex ":" M "," Address ":" http://www.lvyf.com "" _id ": ObjectId ("575e889880d09b176a58ce66"), "name": "Child", "Age": 2, "Sex": "M", "Address": "Http://www.child.com", "stat US ":" Cry and Laugh "}

(5) combined with and and or, equivalent to where age >= 3 and (name= ' Lvyafei ' or sex= ' M ')

Db.first_col.find ({age: {$gte: 3}, $or: [{name: ' Lvyafei '}, {set: ' M '}]}). Pretty (){    "_ ID ": ObjectId (" 575e879380d09b176a58ce64 "),    " name ":" Lvyafei ",    " age ":    "Sex": "M",    "address": "Http://www.lvyf.com"}

(6) greater than and less than union query, equivalent to where age > 3 and Age < 21

Db.first_col.find ({"Age": {$lt:, $GT: 3}})"_id": ObjectId ("575e880980d09b176a58ce65"), "name": " Chenjl "," age ": +," sex ":" W "," Address ":" Http://www.chenjl.com "}

(7) $type operator

If you want to query that name is a string type of record

> Db.first_col.find ({name: {$type: 2}});" _id ": ObjectId (" 575e879380d09b176a58ce64 ")," name ":" Lvyafei "," age ": +," sex ":" M "," Address ":" Http://www.lvyf.com "_id": ObjectId ("575e880980d09b176a58ce65"), "name": "Chenjl", "age": +, "sex": "W", "Address": "Http://ww w.chenjl.com "_id": ObjectId ("575e889880d09b176a58ce66"), "name": "Child", "Age": 2, "Sex": "M", "Address": "Http://www.child.com", "status": "Cry and Laugh"}

mongdb--3. Query operations