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A VALUES in MySQL Auto_Increment is an auto-incrementing variable that helps provide a unique identification for a set of data in a table. It is most commonly used PRIMARY in a key to uniquely index a row. In MySQL, we can AUTO INCREMENT ap...

The PostgreSQL official documentation states, ``LATERAL 关键字可以位于子 SELECT FROM 项之前。这允许子 SELECT 引用出现在 FROM 中的 FROM 项的列（如果没有 LATERAL ，每个子 SELECT 都是独立评估的，因此不...

USERNAME Many PostgreSQL users may be asked for their database settings for the first time when logging in PASSWORD . However, just learning these settings is not all you need to know. What is the server in Rails 4? The server in Rails 4 us...

PSQL is a terminal-based front-end for the PostgreSQL database server. It uses either command-line arguments from an input file or from the command line, and is portable and easy to use. It also helps in writing scripts and letting other ta...

Before we start looking at different solutions to this problem, let's understand what a CSV file is and how output works in PL/pgSQL. PL/pgSQL output is the data displayed after running certain types of queries in PostgreSQL. Sometimes, as...

Let's start with a simple question. INFORMATION_SCHEMA What exactly is it? INFORMATION_SCHEMA Provides us with information about the objects defined in our database. It contains a set VIEWS of objects that store QUERY the database objects....

This article will use the PostgreSQL database to show the different commands we can use to return a collection of database tables. MySQL A common command you will encounter in databases is , SHOW TABLES but in PostgreSQL, the database manag...

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...

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...

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...

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, 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...

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...

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...

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...