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This article describes how to rename a column and change its type in PostgreSQL using only a single query. Renaming and changing column types in MySQL In MySQL , if you want to change the column type and rename it, you can use a simple stat...

In this article, we will learn how to terminate a PostgreSQL session. Any open connections are run by background processes or tasks, PSQL which may no longer exist despite exiting the user interface or command line tool. Use ps -ef or grep...

We will learn about different ways to copy data from one database to another. This strategy of replicating data 数据复制 is very useful in . Due to data replication, data can be served to different servers and made available to all user...

In this tutorial, we aim to explore how to set NULL the value in MySQL. If there is no value, then the specific table field in MySQL has to be updated NULL . This NULL value addition helps in data storage, accessibility, and analysis. You m...

This tutorial explains the refresh permissions operation and its implementation with examples. Implementing refresh permissions in MySQL MySQL implements user management through grant tables to ensure security and access control in the serv...

This tutorial shows you how to reset the auto increment in a MySQL table. Most businesses and organizations using MySQL need to insert values ​​into multiple tables simultaneously. While it is not possible to make all fields of the inse...

IN Today, we will take a closer look at how the and ANY operators work in PostgreSQL . However, remember that both are standard SQL operators, which means we can use them on multiple management platforms. By looking at them one by one and t...

This article will introduce PostgreSQL INSERT ON DUPLICATE UPDATE . 插入重复更新 What does it mean? Why should I use it? Whenever you add 插入 a record to the table, you add 主键 a data set with a unique ID. It can be a different...

Last time, we read about how to use it in PostgreSQL UPSERT . In a quick review, UPSERT is short for , which tends to insert values ​​into the table INSERT ON DUPLICATE UPDATE if they don't match a previous entry . If they do, they are...

ON DELETE CASCADE Before we start looking at different solutions for implementing in PostgreSQL , we will first understand ON DELETE CASCADE what is and what it does. Let's assume you have two tables, one of which inherits from a parent tab...

In our article, we mainly work on the PostgreSQL application called pgAdmin [app. number] , which can be downloaded from the PostgreSQL website. Therefore, we hope that you already have the application installed or another alternative where...

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...

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....