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In this tutorial article, we will explain how to declare variables in SQL code for MySQL database. In SQL scripts, you can use variables to store values ​​and use them in place of literals during the execution of a series of commands. U...

Summary: in this tutorial, we will learn how to shuffle or sort the values ​​or records of a table in MySQL. Most businesses and organizations that use MySQL for data analysis or visualization need to sort different table values ​​o...

This tutorial aims to understand unsigned in MySQL. unsigned Using keywords in MySQL Businesses and organizations have to assign data type as unsigned for certain columns. However, it is important to understand when and where to use this da...

Traditional SQL INSERT statements do not perform input validation of their parameters/values ​​against existing database tables, which sometimes results in errors when duplicate keys are found during the insert process. This is handled...

This tutorial discusses how to check for duplicates in a MySQL table and retrieve the number of duplicates using the SELECT DISTINCT and statements, respectively. SELECT COUNT SELECT DISTINCT Check for duplicates in a MySQL table using The...

mysqld Is a daemon server program, also known as MySQL server. It is used to manage the MySQL data directory with tables and databases. This tutorial guides you through the various methods you can use to start, stop, or restart a MySQL serv...

This tutorial will guide you through creating a MySQL EVENT timer, also known as a MySQL timer. We will see how to set a timer in MySQL to let MySQL manipulate the data (eg. UPDATE // data) INSERT . DELETE It will also take a backup (if req...

This tutorial will teach you how to mysqldump export a MySQL database using the export utility. We will see mysqldump the syntax of using , its parameters and reasons to use it. We will also practice this utility by taking backup with/witho...

In some cases, users want to capture the operations in an output file or some local storage. The storage can be a CSV file or a notepad where the contents of the SQL can be placed. outfile This file is generated using the MySQL command. Thi...

Today, we will learn 等待表元数据锁定 . This article focuses on the causes of metadata lock waits and provides solutions. What are locks in MySQL? A lock is a mechanism associated with a table to restrict unauthorized access to the...

There are many articles about finding the last inserted ID of a table in MySQL. However, it is hard to find any tutorials about finding the last inserted ID using two tables. In this article, we will try to solve this special case, and of c...

Today's tutorial is an introduction to MySQL composite keys. This lesson also discusses the use of the CREATE and ALTER statements to create composite primary and foreign keys. Introduction to MySQL composite keys A composite key is a type...

In this article, we will introduce MySQL comments. We will also understand what type of comments should be used and where. Comments are written to describe the code and make it easier to understand. We also use comments to ignore a part of...

In this article, we will learn about escape sequences. We will look at its definition with examples and sample code. We'll also explore how to use it with wildcards to find patterns in your data. Definition of escape sequences An escape seq...

当你需要在 MySQL 中的脚本中存储单个值时，最好的方法是使用变量。变量有不同的种类，有必要知道何时以及如何使用每种类型。...