MySQL User defined variables and System variables defined variables

Question: What are User-Defined Variables in MySQL?
User-Defined variables are variable that defined by user as per there need. Once they exit from the console, will be removed automatically.


Question: How to set User-Defined Variables in MySQL?

set @name="this is new variable";

Question: How to get User-Defined Variables in MySQL?

select @name;

Question: Can we define multiple variable in single line?
Yes, We can.

set @num1=10, @num2=20, @num3=30;

Question: Can we do arithmetic operators on variable?
Yes, we can do.

select @num1+@num2+@num3; //60
select @num1+@num2+@num3; //6000

Question: Is user defined variable are permanent?
No, It will be removed once close the session.


Question: Can we use user variable with Query?
Yes, If you have defined in same session, then you can use.


Question: What are System Variables?
System Variables explains how your MySQL server are configured and you can change as per your requirement.


Question: How to get the value from system variable?

select @@max_connections; //100

Question: How to update the value from system variable globally?

set @@global.max_connections=200;

set GLOBAL @@max_connections=200;

Best Related Posts are Following:

1. What is Stored Procedure in MySQL?.
2. How to get the sizes of the tables in mysql database?.
3. How to install and Connect to MySQL in NodeJS?.
4. What is Super Key, Candidate keys and Alternate Key?.
5. MySQL Query Optimization Tips and Techniques.
6. How can I make SQL Query case sensitive string comparison on MySQL?.
7. Comparison between MySQL and MongoDB.
8. DBMS Interview Questions and Answers for Freshers.
9. MySQL Interview Questions and Answers for Experienced.
10. Difference between inner join and outer join in MySQL.
11. How to get a list of MySQL user accounts?.
12. How to delete MySQL Binary logs Files in Wamp Server?.
13. SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 2269548 for key PRIMARY.
14. Multiple column ordering in Zend Framework.

Heroku tutorial - Basic understanding

Question: What is Heroku?
Heroku is a cloud "platform as a service (PaaS)" supporting several programming languages that is used as a web application.


Question: Can we deploy the PHP Project in Heroku?
Yes, you can do. You can even deploy Java, nodeJs, Python and Go project also.


Question: What other programming language it support?

Ruby programming
Java 
Node.js
Scala
Clojure
Python
PHP
Go

Question:How many Apps created on Heroku?
13 million.


Question:How many services Heroku have?
150+ Add-on Services


Question: Is Heroku secure?
Yes, It is.


Question: What Heroku does?
Heroku is a platform for data as well as apps - providing a secure, scalable database-as-a-service.
It is million of developers tools like database followers, forking, dataclips and automated health checks.

Question: What is offical website of heroku?
https://www.heroku.com/


Question: What are the steps to configure PHP Project?

1. Introduction: Installed PHP, composer locally.
2. Set up: a) Download the heroku CLI.
   b) Installed the CLI with Git.
   c) Login with heroku account.
3. Prepare the app
4. Deploy the app
5. View logs
6. Define a Procfile
7. Scale the app
8. Declare app dependencies
9. Push local changes
10. Provision add-ons
11. Start an interactive shell
12. Define config vars
13. Provision a database