Table is the main form of data storage in database. It is composed of rows and columns, which is similar to common spreadsheet.The biggest difference between tables in MySQL and other databases is that they can use different storage engines. Storage Engine is a component used to manage, access and modify physical data in MySQL. Different storag ...
Posted by nite4000 on Mon, 08 Nov 2021 09:19:07 -0800
Relatively speaking, the writing is fairly complete. Basically, that's all you can use in your work. A good brain is better than a bad pen. Stored procedures, stored functions, engines, transactions, scheduled tasks, triggers, variables and so on are included. You can collect those you are interested in!
1. Connect to mysql
mysql is divide ...
Posted by david.brown on Mon, 08 Nov 2021 07:38:52 -0800
Blind injection, as the name suggests, means that the return value can not be seen directly during injection, but we can judge it by other methods: next, I will introduce error echo, time blind injection and Boolean blind injection one by one.
Blind injection is divided into three categories:
reference resources: like 'ro%' # judge whe ...
Posted by noisenet on Sat, 06 Nov 2021 13:54:55 -0700
(31) create a view of information department student information
create view IS_Student
where sdept = 'IS';
(32) query students younger than 20 years old in the student view of the information department
where Sage < 20;
(33) delete all course selection records of Ma Chaoyang
Posted by buceta on Fri, 05 Nov 2021 13:18:46 -0700
Basic introduction and configuration
Video link #Crazy God said sql
Query data storage place
Start service + enter database management system
1 – start local mysql service
computer management system command line
net stop/start mysqllin
2 – enter the management system with the password Username root password 12345 ...
Posted by xdentan on Fri, 05 Nov 2021 10:47:01 -0700
MySQL34 homework questions
1. Name of the person who gets the highest salary in each department
mysql> select e.ename,t.* from emp e join (select deptno,max(sal) as maxsal from emp group by deptno) t on t.deptno = e.deptno and t.maxsal = e.sal;
| ename | deptno | maxsal |
| BLAKE | ...
Posted by leena86 on Wed, 03 Nov 2021 18:07:17 -0700
To be honest, the concept of artificial intelligence is somewhat too large, including in-depth learning, machine learning, intensive learning and so on, while in-depth learning includes image recognition, speech recognition, natural language processing, prediction analysis; Machine learning includes supervised learning, unsupervised learning an ...
Posted by dilum on Tue, 02 Nov 2021 12:33:53 -0700
Station B Laodu - Introduction to MySQL
DQL data query language
Simple query (query a single field)
select Field name from Table name;
//Field name and table name are identifiers, and select and from are keywords
//Stress: it is common for sql statements. sql is not case sensitive, and ';' ending
// Chinese aliases need to be enclosed in quot ...
Posted by sebjlan on Sun, 31 Oct 2021 20:13:45 -0700
1, Aggregate query
1. Aggregate function
Common aggregate functions can be used to count the total number and calculate the average value. Common aggregate functions include:
These functions are relatively simple and can be understood through several SQL statements
-- How many students are there in the table
select count(*) f ...
Optimization of 20 SQL statements with twice the result with half the effort
1. Use the where condition to limit the data to be queried to avoid returning redundant rows
Suppose the business scenario is to query whether a user is a member
List<Long> userIds = sqlMap.queryList("select userId from user where isVip=1 ...
Posted by edking1 on Sun, 31 Oct 2021 13:51:16 -0700