MySQL

Chapter 13th grouping DataThis chapter describes how to group data so that you can summarize subsets of table content. This involves two new select sentence sentences, the GROUP BY clause and the HAVING clause, respectively.13.1 Data groupingAs you

I. Using SQL hintsSQL hint (SQL hint) is an important means to optimize the database, is to add some artificial hints in the SQL statement to achieve the purpose of optimization operations.1.1 Use IndexAfter the table name in the query statement,

Note: Original address: https://www.cnblogs.com/hezhuoheng/p/9366630.htmlThe most important of these is the three principles: the command entered in sequence, removed the INI (this is not a principle, it is a way for me to solve the problem), to

a thingTransactions are used to manipulate multiple SQL for some operations as atomic, and once an error occurs, it can be rolled back to its original state, guaranteeing database data integrity.CREATE table user (ID int primary key

Resolve the issue in 1:mysql Import the SQL file.Step 1:show databases; #看看我有什么数据库Step 2:use hh; #我要用hh这个数据库, return to database changed instructions open successfully.Step 3:show tables; #看看hh这个数据库里面有那些表Step 4:source

16th-Create an advanced junctionThis chapter explains the other types of joins (including their meanings and how to use them), and describes how to use table aliases and aggregate functions for joined tables.16.1 Using table AliasesThe 10th chapter

One, stored procedures1, definition: A set of programmable functions, is to complete a specific function of the SQL statement set, compiled and saved in the database, the user can specify the name of the stored procedure and given parameters (when

Installation process: Initialization 解压安装包之后，在根目录创建文件：my.iniMy.ini[mysqld]# 设置3306端口port=3306# 设置mysql的安装目录basedir=D:\\2-software\\01-back-end\\mysql-8.0.11-winx64 # 切记此处一定要用双斜杠\\，单斜杠我这里会出错，不过看别人的教程，有的是单斜杠。自己尝试吧#

First, the successful index optimization 1. The table data is as follows: 2. The query statement is as follows: Explain select ID, age, level from employee where Dpid = 1 and age = of order BY Extra:using where; Using Filesort

Use the show statement to find out what database currently exists on the server: show DATABASES;Create a database abccs:create databases test12;Select the database you created: Use test12Creating a database table: CREATE table student ();We want to

The traditional operations in relational data operations--and (UNION), Cartesian product (Cartesian product), connection (join).1. and (UNION)" and " is to merge tables with the same number of fields and the same field type.Number of records merged =

#!/bin/bashuser= "root" password= "root" mysql= "/usr/mysql/mysql-5.6.10/client/mysql" host= "10.198.18.18" Thread_ status=$ ($MYSQL  -u "$USER"  -p "$PASSWORD"  -h "$HOST"  -e  ' show slave status\g ' |GREP-IYES|WC-L) status= ($ ($MYSQL  -u "$USER"

One, why use trigger 1. What is a trigger Triggers are one of the MySQL database objects that need to be declared, executed, etc., the execution of the trigger is not called by the program, nor is it started manually, but is triggered and

First, insert data recordTipDesc table_name 查看表信息及字段类型避免插入类型不一致。1. Insert full data recordBasic syntaxINSERT INTO table_name( field1, field2, field3, ......fieldn) VALUES( value1, value2, value3, ......valuen) OrINSERT INTO table_name

The first step, download MySQL1, Address: https://dev.mysql.com/downloads/mysql/2. Version: Mysql-8.0.11-winx64.zipSecond step, decompression Modify/Create configuration file1. If you want MySQL to be installed in the specified directory, then move

Stored ProceduresDefinition of a stored procedureSecond, the advantages of stored proceduresThird, the use of stored procedures3.1 Creation and invocation of stored procedures3.2 Viewing and deletion of stored proceduresThe definition of a stored

Grant all privileges the test_db.* to [e-mail protected] identified by ' 123456 ';Grant all on test_db.* to [e-mail protected] identified by ' 123456 ';Grant Select,insert,update,delete on * * to [e-mail protected] "%" identified by ' 123456

Using the master-slave replication technology provided by MySQL itself, in the enterprise production scenario, it is possible to make multiple automatic backups of the log data, and realize the expansion of the database. For example, in a scheduled

30th-Improving performanceThis chapter will review some of the key points related to MySQL performance.30.1 Improving performanceDatabase administrators spend a considerable portion of their lives tuning, experimenting to improve DBMS performance.

19th Chapter-Inserting dataThis chapter describes how to insert data into a table using an INSERT statement from SQL.19.1 Data InsertionThere is no doubt that select is the most commonly used SQL statement (which is why the first 17 chapters are