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

MySQL database functions

1, Date and time functions 1. Function to get the current dateIt's the same. It's different CURDATE() : Used to get the current date of the system CURRENT_DATE() Used by the system to get the current date mysql> select CURDATE(),CURRENT_DATE(); 2. Get function of current time CURTIME() : Used to get the current time of the system mysql& ...

Added by brighton on Thu, 14 May 2020 12:11:49 +0300

Issue 04: column CHECK constraint

check constraint means to filter one or more columns according to certain preset rules. If the condition is true, the filtering succeeds; if the condition is false, the filtering fails and the failure code is returned to the client. Why do you want to list and write this separately? You often encounter irregular SQL. In many cases, you can onl ...

Added by AndyB on Wed, 13 May 2020 12:25:22 +0300

My first JDCB program

1, Create your own database Download and install MySQL 1.windows Download: http://dev.mysql.com/downloads/mysql/ 2. Open the server: enter the bin directory of the download path in the terminal (cmd), and execute mysqld -- initialize executor to start the server and initialize, but an error will be reported. The reason is that there is no data ...

Added by _giles_ on Mon, 11 May 2020 07:51:35 +0300

Database learning 7: MySQL client tools and SQL introduction

7, MySQL client tools and SQL introduction 1. Syllabus: mysql client command introduction; How to get help from mysql; Management database of DDL statements; DDL statement management table and case introduction; Data in management table of DML statement; SELECT to retrieve data; 2. mysql interface program and SQL introduction mysql client comma ...

Added by jdimino on Fri, 08 May 2020 16:47:04 +0300

Using Blink SQL+UDAF to realize difference aggregation calculation

According to the real business requirements of a power grid company, this case realizes the difference aggregation calculation on the real-time flow through Blink SQL+UDAF. Through this case, the readers are familiar with UDAF writing and understand the method invocation relationship and order in UDAF. Thank you @ commander for your guidance in ...

Added by stalione on Fri, 08 May 2020 12:15:27 +0300