迹忆客 EN >

数据库连接 A string is an expression in which there are all the parameters necessary to establish a connection from a terminal device to a database. It contains databases 用户名 , 密码 , 名称 , 主机地址 and 端口 . This con...

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...

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...

MySQL PostgreSQL is an object-relational database system, which means it can support more complex data types than its competitors . Today we will learn how to use SELECT the operator to join the columns of a table. Using operators to || joi...

This article shows how to use the statement in PostgreSQL CASE . CASE How to use the statement in PostgreSQL case Statements are similar to those in general-purpose programming languages if-else . But in SQL, if you want to write IF-ELSE ,...

NOT IN The inverts the result of NOT simply using IN the operator. NOT IN The right side of the operator must have a subquery in which multiple columns are returned to check whether the expression matches the data. NOT IN Tends to return tr...

This article will demonstrate how we can declare and assign values ​​to variables in PostgreSQL. In PostgreSQL, DECLARE variables are declared using Often you will need variables in your PL/SQL scripts. In DECLARE the section called , y...

This article shows various ways to connect to PostgreSQL using a password. It can be through the command line, pgpass a file, PGPASSWORD an environment variable or a connection string. Connecting to PostgreSQL with a password using the comm...

There are two ways to access PostgreSQL objects and databases on your system. One is through an interface, such as a graphical interface like PGADMIN, and the other is the basic command line tool psql. Today, we will look at DROP DATABASE t...

This article demonstrates connecting to a database, creating a new database, and creating a table in PostgreSQL. Available databases in PostgreSQL You can run the following command after opening the Postgres command line to view all availab...

This article discusses how to use PostgreSQL replace() functions to replace strings. Use the PostgreSQL replace() function to replace strings PostgreSQL replace() functions have the following arguments, which are all text types: replace (st...

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...

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....

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...

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...