Aggregate operators of [LINQ standard query operator summary]

LINQ in C ා provides two operation modes: query expression and query operator. All query expressions are replaced by corresponding query operator classes. Query expression is a bit of "class" SQL. When writing SQL in the code, I always feel that it is not "elegant". Using query operators is "elegant". This series i ...

Added by nloding on Sat, 30 May 2020 17:01:17 +0300

PHP and Thinkphp simulated message board to deal with XSS attack (super complete!)

XSS attack principle and protection brief introduction XSS(Cross Site Scripting) is a common way in Web attacks. Through this attack, users can be controlled to do a series of malicious operations, such as stealing, tampering, adding users' data or inducing to phishing sites. Attack principle A common way is to use unfiltered parameters to pass ...

Added by Nothsa on Thu, 28 May 2020 07:50:18 +0300

Introduce mybatis-plus to report an Invalid bound statement error. Move your finger to change one place

error Mybatis-Plus (MP) is an enhancement tool for mybatis. On the basis of mybatis, only enhancements are made without changes, which simplifies the development efficiency.This is to help us encapsulate some simple curd methods that can be called directly without rewriting these simple sql statements, just like JPA. A new project was created t ...

Added by zenix on Thu, 28 May 2020 06:02:40 +0300

[12c] let you know the collection of Extended Statistics of Oracle 12c database

In the Oracle database, the optimizer needs to rely on the collection of statistical information of related objects in order to generate the optimal execution plan. The database can automatically collect the execution plan or use the package DBMS_STATS is collected manually. This article does not explain the collection of general statistics. It ...

Added by libertyct on Wed, 27 May 2020 15:38:34 +0300

C ා data operation series - 16 SqlSugar conclusion

0. Preface In the previous article, we introduced the addition, deletion, modification and query of SqlSugar in detail, which has satisfied our use in daily engineering development. However, there are a few methods that are not commonly used in development, but are very useful. Let's see what else is interesting. 1. Unusual query Previously, we ...

Added by paullb on Tue, 26 May 2020 11:22:24 +0300

Optimistic Lock (CAS) retry data version not updated under mysql transaction default isolation level

Exception Information Ccom.mysql.cj.jdbc.exceptions.MySQLTransactionRollbackException: Lock wait timeout exceeded; try restarting transaction Reasons for the problem When optimistic locks modify data, the data version number has been modified, causing the modification to fail. When retrying the modification, each time the data read from the d ...

Added by xsist10 on Fri, 22 May 2020 21:51:58 +0300

oracle uses stored procedures for row to column conversion (executing dynamic SQL statements)

---------------------------------------------------------------Table building----------------Determine whether the student table exists declare num number; --Declare parameters num type number begin --start select count(1) into num from user_tables where table_name='student'; if num>0 then execute immediate 'drop table st ...

Added by crinkle on Thu, 21 May 2020 18:21:15 +0300

Basic usage of JDBC

JDBC fixing steps: Load driver String url="jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT"; String username="root"; String password="123456"; Class.forName("com.mysql.cj.jdbc.Driver");//I don't know why com.mysql.jdbc.Driver will report an error. Please leave a message if you have any ...

Added by PHPfolife on Wed, 20 May 2020 17:31:54 +0300

Introduction to Connection-Control for MySQL

In Oracle and SQL Server databases, you can set up some complex account password policies, such as locking an account more than N times after a failed login, so can you do the same in MySQL?The answer is that MySQL has similar capabilities, except in MySQL it delays the response time when its login fails beyond the threshold, instead of locking ...

Added by marco839 on Tue, 19 May 2020 20:23:28 +0300

C ා data operation series - 7. EF Core navigation attribute configuration

In the previous article, I introduced the logic of relationship mapping in Entity Framework Core. The foreign key mapping of EF left in the previous article is not mentioned, that is, the relationship of one-to-one, one to many, many to one, many to many, etc. This article will give you a detailed analysis of how to set up these mappings. 1. Re ...

Added by imawake on Sun, 17 May 2020 08:59:50 +0300