In one of the recent programming job interviews, one of my readers was asked the question, how do you join two tables which are not related to each other? i.e. they don't have any common column? is it possible in SQL? My reader got confused because he only knows about INNER join and OUTER join which require a key column like dept_id which is the primary key in one table like Department and foreign key in another table like Employee. He couldn't answer the question, though he did tell them about you can select data from multiple tables by typing multiple table names in from clause using a comma.
Difference between Primary key vs Candidate Key in SQL Database? Example
Primary key vs Candidate Key
What is the difference between primary key and candidate key is another popular SQL and database interview question which appears in various programming interviews now and then? The concept of primary key and candidate key is not just important from the interview point of view but also in designing databases and normalization. By the way, this is my second post about primary keys, In the last one, we have seen a comparison of primary key vs unique key, which also happens to be one of the frequently asked database questions.
Difference between Clustered and Non-Clustered Indexes in Database? SQL Question Answer
Clustered vs Nonclustered Indexes in SQL
The difference between Clustered and Nonclustered index in a relational database is one of the most popular SQL interview questions almost as popular as the primary key vs unique key, the difference between truncate and delete, and correlated vs noncorrelated subqueries. Indexes are a very important concept, it makes your queries run fast and if you compare a SELECT query which uses an indexed column to one who doesn't you will see a big difference in performance.
The difference between Clustered and Nonclustered index in a relational database is one of the most popular SQL interview questions almost as popular as the primary key vs unique key, the difference between truncate and delete, and correlated vs noncorrelated subqueries. Indexes are a very important concept, it makes your queries run fast and if you compare a SELECT query which uses an indexed column to one who doesn't you will see a big difference in performance.
Difference between Primary key vs Unique key in SQL Database? Answer
primary key vs unique key in SQL
The primary key and unique key are two important concepts in a relational database and are used to uniquely identify a row in a table. Both primary key and unique keys can identify a row uniquely but there is some subtle difference between them which we will see in this article. In fact, primary key vs unique is a popular SQL interview question along with classics like truncate vs delete and How to manage transactions in a database, mostly asked to fresher and 2 to 3 years experience guys in any programming language. SQL is not just limited to any DBA or PLSQL developer but it's an important skill even for Java programmers and you can expect SQL interview questions even in many Java interviews.
The primary key and unique key are two important concepts in a relational database and are used to uniquely identify a row in a table. Both primary key and unique keys can identify a row uniquely but there is some subtle difference between them which we will see in this article. In fact, primary key vs unique is a popular SQL interview question along with classics like truncate vs delete and How to manage transactions in a database, mostly asked to fresher and 2 to 3 years experience guys in any programming language. SQL is not just limited to any DBA or PLSQL developer but it's an important skill even for Java programmers and you can expect SQL interview questions even in many Java interviews.
Top 10 tools for SQL Developers and Database Administrators
Hello guys, if you are a SQL database administrator a SQL Developer, a good knowledge of database tools can really help. It even been said that a craftsman is as good as his tools. So, you should spend some time and find out the tools which can help you with your job with respect to Database and SQL. Here are the main 10 free data set instruments that play out a great many explicit capabilities. The thought behind this rundown is to assist you with picking the right devices that best met your requirements.
Top 5 Online Courses to Learn MySQL Database in 2025 - Best of Lot
Hello guys, if you want to learn MySQL and SQL in 2025 and looking for the best resources like online courses, tutorials, and books then you have come to the right place. Earlier, I have shared the best SQL courses, books, and SQL interview questions and today, I am going to share the best online courses to learn MySQL in 2025. As you most probably know, MySQL is one of the big players in the Big Data technological ecosystem. It is one of the most popular databases in the world and has wide-ranging capabilities. It is used in a wide variety of industries, and so every half-decent programmer should at least have a basic understanding of MySQL.
Top 5 PostgreSQL Courses and Tutorials for Beginners in 2025 - Best of Lot
Hello guys, if you want to learn PostgreSQL and looking for the best resources like online courses, books, and tutorials then you have come to the right place. In the past, I have shared the best online courses to learn MySQL, Oracle, SQL Server, and SQL in general, and in this article, I am going to share the best online courses to learn PostgreSQL from Scratch. If you don't PostgreSQL is one of the popular databases and used by many companies in production It is an open-source, object-relational database system that has been around for more than 15 years. It has a strong reputation for reliability, stability, and data integrity.
How to solve Arithmetic overflow error converting IDENTITY to data type tinyint, smallint or int in Microsoft SQL Server database
Last year we had a production issue where one of our backup jobs was failing while inserting Orders aggregated from other systems into our SQL Server database. The reason was dreaded "Arithmetic overflow error converting IDENTITY to data type int" because the table was using IDENTITY feature of SQL Server to generate OrderId, and Identity has breached it a maximum value, which is around 2.1 billion, precisely 2,147,483,647. The error "Arithmetic overflow error converting IDENTITY to data type int" comes when the IDENTITY value is inserted into a column of data type int, but the value is out-of-range. For example, if the current value of Identity becomes more than 2,147,483,647, then you cannot store that into an int column because it's more than the maximum value of int in SQL Server.
How Long It Take To Become a DBA (Database Administrator) in 2025?
Hello guys, if you want to become a Database Administrator in 2025 and wondering how long does it take to learn SQL and Database and become a professional Database Administrator or Junior DBA then you are at right place. In the past, I have shared free SQL and Database courses as well roadmap to become a Web Developer and in this article, I am going to share how long it will take you to become a DBA in 2025. Along the way, I will share best way to learn SQL and Database and what is the best way to become a DBA quickly. So continue reading and find out what it takes to become a DBA and get a job in real world. I will also share all the skills you need to become a DBA in 2025.
Top 6 Free Database and SQL Query Courses for Beginners to Learn Online in 2025 - Best of Lot
Hello guys, I have been sharing some free programming resources e.g. books and courses in this blog for quite some time. Earlier I have shared free courses on Java, Maven, Spring, and Data Structure and Algorithms and today I'll share some of the free online training courses to learn SQL and Database. Why you should learn SQL? Well, it's one of the must-have skills for programmers, application developers, and IT professionals. Like Linux, this is one skill that is going to serve you longer than any other programming language, framework, or library.
Top 6 SQL and Database Courses on Udemy + Coursera in 2025 - Best of Lot
Hello guys, if you want to learn SQL and Database and look for the best Udemy courses, you have come to the right place. Earlier, I have shared the best free SQL courses, which contain free courses from Udemy and Coursera, and other websites. This article will share the best SQL courses from Udemy, suitable for beginners and intermediate developers. SQL has been a vital tech skill for a long time, but with the advent of Data Science and Data Analysis, the importance of data has made it even more critical in today's world.
Top 5 Free MongoDB and NoSQL courses for Beginners to Learn in 2025 - Best of Lot
If you want to learn MongoDB in 2025, one of the most popular NoSQL databases and are looking for free resources like free tutorials and free online MongoDB courses to start with, you have come to the right place. Earlier, I have shared the 10 free full-stack development courses, and today, I will share the 5 best free online courses to learn Mongo DB online. These courses are created by experts and made free for educational purposes. Thousands of students have already joined these free Mongo DB courses, and you can also do the same to learn this in-demand skill and further boost your resume for cutting-edge jobs.
Top 10 Oracle Database and PL/SQL Courses for Beginners in 2025 - Best of Lot [UPDATED]
Hello folks, if you are learning Oracle database and want to learn PL/SQL programming language and looking for the best resources like books, online courses, tutorials and articles then you have come to the right place. In the past, I have shared the best free SQL and database courses, PL/SQL books, and a few free Oracle courses, and this article will introduce you to the Oracle SQL database and how they work as well as the PL language and how you can use its commands to interact with the oracle SQL database in 2025.
5 Best DP-900 Certification Courses and Practice Test for Azure Data Fundamentals Exam in 2025
The DP-900 certification, also known as the Microsoft Azure Data Fundamentals Certification, is perfect for people who are just starting to work with data on the cloud. This certification will help you build foundational knowledge in cloud data services with Microsoft Azure. Taking the DP-900 certification exam will have many benefits. It will give you a broad overview of how data works in the cloud. It will also help you test your knowledge of cloud data within the ambit of Microsoft Azure services.
How to use DROP command to remove tables in Oracle, MySQL and SQL Server
Hello guys, if you want to learn about DROP command in SQL then you have come to the right place. Earlier, I have shared the best free SQL and Database courses and several tutorials to learn SELECT, GROUP BY, and other important commands, and in this article, I will show you to use the DROP command in SQL. DROP is one of the basic SQL commands, which is used to DROP database objects. Since it's part of ANSI SQL, the DROP command is supported by all major database vendors, including Oracle, MySQL, and Microsoft SQL Server. A SQL DROP TABLE statement is used to delete a table definition and all data from a table, but DROP can also be used to drop index, view, trigger, or any other database object.
[Solved] Caused by: java.sql.SQLSyntaxErrorException: ORA-01722: invalid number in Java and Oracle
Hello guys, if you are getting below error in your Java program and wondering how to solve this or just stuck then you have come to the right place. In this article, I will explain to you what causes the " java.sql.SQLSyntaxErrorException: ORA-01722: invalid number" error when you connect to an Oracle database from a Java program and how you can solve it.
But, first of all, let's take a look at the stack trace of this error which looks like below:
10 Essential SQL Commands and Functions Every Developer should learn
Hello guys, if you are starting with SQL and wondering which commands you should learn first then you have come at the right place. In this article, I have shared 10 most essential SQL commands and functions which I believe every programmer should learn. This includes commands to pull data from database as well write data into data, update data, and remove data from database. While writing in the SQL language, you will utilize an assortment of SQL keywords to make explanations and questions. An assertion includes a series of characters and SQL keywords that adjusts to the designing and grammar rules of the language and may influence information or control processes corresponding to your information.
How to convert String to Integer SQL and Database? MySQL, Oracle, SQL server and PostgreSQL Example
Hello guys, if you are wondering how to convert VARCHAR to String in SQL then you are at the right place. In this article, we will cover various techniques to convert String to Integer in all databases - MySQL, Oracle, SQL server and PostgreSQL. To perform tasks or correlations or change between information in a SQL Server data set, the SQL information kinds of those values should coordinate. At the point when the SQL information types are unique, they will go through a cycle called type-projecting. The transformation of SQL information types, in this cycle, can be implied or unequivocal.
What is Normalization in SQL? 1NF, 2nd NF, 3rd NF and BCNF Example Tutorial
What is Normalization?
Normalization is one of the essential concept of relational database. It is the process or technique to remove duplicate data from tables and thus reduce the storage size. It also helps to maintain integrity of data. Normalization likewise assists with coordinating the information in the data set. It is a multi-step process that sets the information into even structure and eliminates the copied information from the relational tables. Normalization coordinates the segments and tables of a data set to guarantee that data set integrity constraints appropriately execute their conditions. It is an orderly method of deteriorating tables to take out information overt repetitiveness (redundant) and unfortunate qualities like Insertion, Update, and Deletion anomalies.
What is temporary table in Database and SQL? Example Tutorial
Hello folks, if you have heard the term temporary table online or by your colleague in a call and wondering what is temporary table, what is the difference between a normal table and a temporary table, and when and how to use it then you have come to the right place. In this blog, we shall learn how to use a temporary table in SQL. But before we go into that we need an overview of SQL. What is SQL? SQL stands for Structured query language. it is a programming language used in communicating or relating to the relational database. And this programming language performs various forms of operation in the data. It was created in the 1970s, SQL is used by database administrators, and developers writing data integration scripts, etc.
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