mongodb与mysql命令对比
传统的关系数据库一般由数据库(database)、表(table)、记录(record)三个层次概念组成,MongoDB是由数据库(database)、集合(collection)、文档对象(document)三个层次组成。MongoDB对于关系型数据库里的表,但是集合中没有列、行和关系概念,这体现了模式自由的特点。
MySQL | MongoDB | 说明 |
mysqld | mongod | 服务器守护进程 |
mysql | mongo | 客户端工具 |
mysqldump | mongodump | 逻辑备份工具 |
mysql | mongorestore | 逻辑恢复工具 |
db.repairDatabase() | 修复数据库 | |
mysqldump | mongoexport | 数据导出工具 |
source | mongoimport | 数据导入工具 |
grant * privileges on *.* to … |
Db.addUser() Db.auth() | 新建用户并权限 |
show databases | show dbs | 显示库列表 |
Show tables | Show collections | 显示表列表 |
Show slave status | Rs.status | 查询主从状态 |
Create table users(a int, b int) |
db.createCollection("mycoll", {capped:true, size:100000}) 另:可隐式创建表。 | 创建表 |
Create INDEX idxname ON users(name) | db.users.ensureIndex({name:1}) | 创建索引 |
Create INDEX idxname ON users(name,ts DESC) | db.users.ensureIndex({name:1,ts:-1}) | 创建索引 |
Insert into users values(1, 1) | db.users.insert({a:1, b:1}) | 插入记录 |
Select a, b from users | db.users.find({},{a:1, b:1}) | 查询表 |
Select * from users | db.users.find() | 查询表 |
Select * from users where age=33 | db.users.find({age:33}) | 条件查询 |
Select a, b from users where age=33 | db.users.find({age:33},{a:1, b:1}) | 条件查询 |
select * from users where age | db.users.find({'age':{$lt:33}}) | 条件查询 |
select * from users where age>33 and age | db.users.find({'age':{$gt:33,$lte:40}}) | 条件查询 |
select * from users where a=1 and b='q' | db.users.find({a:1,b:'q'}) | 条件查询 |
select * from users where a=1 or b=2 | db.users.find( { $or : [ { a : 1 } , { b : 2 } ] } ) | 条件查询 |
select * from users limit 1 | db.users.findOne() | 条件查询 |
select * from users where name like "%Joe%" | db.users.find({name:/Joe |

MySQL functions can be used for data processing and calculation. 1. Basic usage includes string processing, date calculation and mathematical operations. 2. Advanced usage involves combining multiple functions to implement complex operations. 3. Performance optimization requires avoiding the use of functions in the WHERE clause and using GROUPBY and temporary tables.

Efficient methods for batch inserting data in MySQL include: 1. Using INSERTINTO...VALUES syntax, 2. Using LOADDATAINFILE command, 3. Using transaction processing, 4. Adjust batch size, 5. Disable indexing, 6. Using INSERTIGNORE or INSERT...ONDUPLICATEKEYUPDATE, these methods can significantly improve database operation efficiency.

In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.

Use the EXPLAIN command to analyze the execution plan of MySQL queries. 1. The EXPLAIN command displays the execution plan of the query to help find performance bottlenecks. 2. The execution plan includes fields such as id, select_type, table, type, possible_keys, key, key_len, ref, rows and Extra. 3. According to the execution plan, you can optimize queries by adding indexes, avoiding full table scans, optimizing JOIN operations, and using overlay indexes.

Subqueries can improve the efficiency of MySQL query. 1) Subquery simplifies complex query logic, such as filtering data and calculating aggregated values. 2) MySQL optimizer may convert subqueries to JOIN operations to improve performance. 3) Using EXISTS instead of IN can avoid multiple rows returning errors. 4) Optimization strategies include avoiding related subqueries, using EXISTS, index optimization, and avoiding subquery nesting.

Methods for configuring character sets and collations in MySQL include: 1. Setting the character sets and collations at the server level: SETNAMES'utf8'; SETCHARACTERSETutf8; SETCOLLATION_CONNECTION='utf8_general_ci'; 2. Create a database that uses specific character sets and collations: CREATEDATABASEexample_dbCHARACTERSETutf8COLLATEutf8_general_ci; 3. Specify character sets and collations when creating a table: CREATETABLEexample_table(idINT

To safely and thoroughly uninstall MySQL and clean all residual files, follow the following steps: 1. Stop MySQL service; 2. Uninstall MySQL packages; 3. Clean configuration files and data directories; 4. Verify that the uninstallation is thorough.

Renaming a database in MySQL requires indirect methods. The steps are as follows: 1. Create a new database; 2. Use mysqldump to export the old database; 3. Import the data into the new database; 4. Delete the old database.


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