How to concatenate columns in SQL Server? Example Tutorial

Hello guys, welcome to my new blog SQLrevisited. I have long back created this blog to exclusively share SQL and Database articles but never get time to start it until today. This is the first article on this blog and in this post, you will learn how to contact multiple columns in an SQL server.  Like Java and many other programming languages and databases, you can use the + operator to concatenate multiple columns in SQL Server. You can join as many columns as you want with the + operator but you must remember that concatenating with NULL will produce NULL, which means you can lose the information from other columns if one of them is NULL. 

Top 6 Free SQL Books For Beginners and Experienced [PDF + Online]

 There is no doubt that SQL is one of the most essential skills for Programmers, IT professionals, Software Engineers, Quality Analysts, Project Manager, Data scientists, Database admins, and Business Analysts. I had even mentioned this as one of the top skills in my post about 10 things every programmer should know, if you haven't read that yet, you can read it here, it's completely worth your time. Since many Enterprise applications use the relational database at their backend, like Oracle, Microsoft SQL Server, MySQL, it's crucial to learn SQL to work with those applications and use the data stored on those databases.

How to join two unrelated tables in SQL? Cross Join Example

 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 UNION and UNION ALL in SQL Server?

 Hello guys, what is the difference between UNION vs UNION ALL is one of the most popular SQL interview questions and often asked programmers during a telephonic round of interviews. Though both UNION and UNION ALL is used to combine results of two SELECT queries, the main difference between them is that UNION doesn't include duplicate record but UNION ALL does. Another difference between them is that UNION ALL is faster than UNION but may look slow because it returns more data which takes more time to travel via the network. The difference between UNION and UNION ALL can be a tricky SQL question, especially for developers, who have not used this useful keyword ever. 

10 Examples of ALTER Table Command in SQL

 In this SQL tutorial, you will learn how to use ALTER command in the table on the database. ALTER command is mainly used to add, modify and drop columns, indexes, and constraints on the table in relational databases e.g. MySQL, Oracle, Sybase, and SQL Server.  Though ALTER is not part of classical CRUD operation but it’s one of the important DDL commands. One of the most frequent uses of ALTER command in SQL is adding and removing indexes to improve the performance of SQL SELECT queries.