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PostgreSQL Articles
Found 20 articles
How To Configure PostgreSQL 12 Streaming Replication in CentOS 8?
Introduction PostgreSQL is one of the most popular open-source relational database management systems (RDBMS). It provides a wide range of features such as data integrity, fault-tolerance, and scalability. One of the essential features in PostgreSQL is Streaming Replication. It allows you to create multiple copies of a PostgreSQL database cluster in near-real-time by continuously streaming the changes from the primary node to the standby nodes. Streaming replication works by streaming the write-ahead log (WAL) data generated by the primary node to one or more standby nodes over a network connection. Configuration of Master Node for Streaming ...
Read MoreHow to Deploy PostgreSQL on Kubernetes?
Introduction PostgreSQL is an open-source relational database management system (RDBMS) known for its robustness, stability, and ability to handle complex and large data sets. On the other hand, Kubernetes is an open-source container orchestration system that automates the deployment, scaling, and management of containerized applications. Combining these two powerful technologies provides a highly scalable and reliable environment for hosting your PostgreSQL database. In this article, we will explore how to deploy PostgreSQL on Kubernetes. We will start by explaining what PostgreSQL and Kubernetes are and the benefits of deploying PostgreSQL on Kubernetes. Then we will go through an overview of ...
Read MoreHow to Remove Unicode from Jenkins Console Output logs using Postman?
We can remove Unicode from Jenkins Console Output logs. To perform this, we should create a Collection with at least a single request. Along with it, we have to install Newman.Step 1 − Click on the arrow appearing to the right of the name of the Collection. After that, click on Share.Step 2 − SHARE COLLECTION pop-up shall open. Navigate to the Get public link tab and copy the link which is pointed out in the below image.Please note − The link obtained is specific to a particular user.Step 3 − Launch Jenkins and go to the Jenkins Job which ...
Read MoreDifference Between MySQL and PostgreSQL
In this post, we will understand the difference between MySQL and PostgreSQL.MySQLIt is a relational database management system.It is the product developed by Oracle Corporation.It is supported by Windows, Mac OS X, Linux, BSD, UNIX, z/OS, Symbian, AmigaOS.It can’t be extended.In this system, the phpMyAdmin tool gives the GUI.Mysqldump and XtraBackup provide backup in MySQL.It provides temporary table.It doesn’t provide a materialized view.It doesn’t provide Data Domain Object to the system.PostgreSQLIt is an object-relational database management system.It was developed by the Global Development Group.It is supported by Windows, Mac OS X, Linux and BSD but not by UNIX, z/OS, Symbian, ...
Read MoreWhat all constraints can be added to a PostgreSQL table?
There are 6 types of constraints that can be generally used with a PostgreSQL table. They are listed and explained below −NOT NULL CONSTRAINTThis is a very common constraint. If there is a particular column that cannot have null values, you add this constraint at the time of table creation. For example, if we create a marks table, which can’t have NULL values for the name, then the table creation command will look like −CREATE TABLE marks( name VARCHAR NOT NULL, roll_no INTEGER, marks_obtained INTEGER );Now, if we try to insert a row into this table, without ...
Read MoreCreate Primary Key on an existing table in PostgreSQL?
Although quite infrequent, you may come across situations wherein you need to define the primary key on an existing table. This can be achieved using the ALTER TABLE statement.The syntax is −ALTER TABLE table_name ADD PRIMARY KEY (column_name1, column_name2, …., columns_nameN)As can be seen from the above syntax, you can define PRIMARY KEY on multiple columns. When you have defined the PRIMARY KEY on multiple columns, the condition is that the column pairs should have unique and non-null values. Thus, if the PRIMARY KEY is defined on (column1, column2), the values (value1, value2), (value3, value2), and (value1, value4) are allowed. ...
Read MoreExtract day, hour, minute, etc. from a datetime column in PostgreSQL?
Let us create a new table containing a single timestamp column −CREATE TABLE timestamp_test( ts timestamp );Now let us populate it with some data −INSERT INTO timestamp_test(ts) VALUES(current_timestamp), (current_timestamp+interval '5 days'), (current_timestamp-interval '18 hours'), (current_timestamp+interval '1 year'), (current_timestamp+interval '3 minutes'), (current_timestamp-interval '6 years');If you query the table (SELECT * from timestamp_test), you will see the following output −ts2021-01-30 19:23:24.0080872021-02-04 19:23:24.0080872021-01-30 01:23:24.0080872022-01-30 19:23:24.0080872021-01-30 19:26:24.0080872015-01-30 19:23:24.008087Now, in order to extract hour, minute, etc. from the timestamp column, we use the EXTRACT function. Some examples are shown below −SELECT EXTRACT(HOUR from ts) as hour from timestamp_testOutput −hour19191191919Similarly −SELECT EXTRACT(MONTH from ts) as ...
Read MoreHow to combine different columns of a table to yield a single column in query output in PostgreSQL?
Suppose you have a table user_info that contains the state and district of different users. An example is given below −namedistrictstateAnilMumbaiMaharashtraJoyJhalawarRajasthanRonPuneMaharashtraReenaMeerutUttar PradeshNow, if you want to combine the state and district in a single field called location, this is how you should be able to do it −SELECT name, district || ', ' || state as location from user_infoThe || operator is the string concatenation operator. The output will be −namelocationAnilMumbai, MaharashtraJoyJhalawar, RajasthanRonPune, MaharashtraReenaMeerut, Uttar PradeshSimilar operations can also be performed on numerical values. Suppose you have a table marks containing the total marks scored by students and the maximum ...
Read MoreHow to look for partial string matches in queries in PostgreSQL?
Suppose you have a table user_info containing the names of users and their addresses. An example is given below −nameaddressAnilAndheri, Mumbai, MaharashtraJoyChandni Chowk, DelhiRonBandra, Mumbai, MaharashtraReenaOld Airport Road, Bengaluru, KarnatakaNow, if you want to just extract the information of users who stay in Mumbai, you can do that using the LIKE command and the % operator.SELECT * from user_info where address LIKE '%Mumbai%'The output will benameaddressAnilAndheri, Mumbai, MaharashtraRonBandra, Mumbai, MaharashtraNotice that we have added % operator on both sides of Mumbai. This means that anything can precede Mumbai and anything can be after Mumbai. We just want the string to ...
Read MoreHow to apply DISTINCT constraint on select columns in queries in PostgreSQL?
Suppose you have a table exam_scores containing 5 columns. An example is given below with some dummy data.nameroll_nosubjecttotal_marksmarks_obtainedAnil1English10056Anil1Math10065Anil1Science10045Roy2English10078Roy2Math10098Roy2Science10067Now, one student could have sat for exams of multiple subjects, and therefore, there are multiple rows for 1 student. If you wish to find out the total number of students in the class, you may want to find the number of distinct values of roll_no. You can apply the distinct constraint on a specific column as follows −SELECT DISTINCT ON (roll_no) name, roll_no FROM exam_scores ORDER BY roll_no DESCHere’s what the output of the above query will look like −nameroll_noRoy2Anil1You can also ...
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