- MariaDB
	https://www.mariadbtutorial.com/getting-started/connect-to-mariadb/
	 
 After installing mariaDB use this command to setup database directory
 `mariadb-install-db --user=mysql --basedir=/usr --datadir=/var/lib/mysql`
 do this `rm -rf /var/lib/mysql/*` to undo this initialization process
  
 To start mariadbd at boot time you have to copy
**support-files/mariadb.service** to the right place for your system
U can do this in systemd init system with
`systemctl enable --now mariadb.service`


  Two all-privilege accounts were created.
One is **root@localhost**, it has no password, but you need to
be system 'root' user to connect. Use, for example, `sudo mysql`
The second is **mysql@localhost**, it has no password either, but
you need to be the system 'mysql' user to connect.
After connecting you can set the password, if you would need to be
able to connect as any of these users with a password and without sudo
 
  See the MariaDB Knowledgebase at https://mariadb.com/kb
  
 	You can start the MariaDB daemon with:
`cd '/usr' ; /usr/bin/mariadb-safe --datadir='/var/lib/mysql'`
   
	You can test the MariaDB daemon with mariadb-test-run.pl
	`cd '/usr/mariadb-test' ; perl mariadb-test-run.pl`
	 
	Please report any problems at https://mariadb.org/jira
	 
	The latest information about MariaDB is available at https://mariadb.org/.
	 
	Consider joining MariaDB's strong and vibrant community:
	https://mariadb.org/get-involved/

- More
  To load mysql shell in command prompt:
    
    `mysql -u root -p`
	  Here root is owner_name. This will prompt for password which is ‘password’.
	  or
	  `mysql -h localhost -P 3306 -u root -p test`
	
	- To connect to remote mysql
	    To connect to MariaDB on a specific host, you use the -h option:

		`mysql -u [username] -p[password] -h [hostname]`
		or to disable ssl check when connecting
		`mysql --skip-ssl  -u proj1_wishrocky -P 3306 -p94db734d1935c57ac05eab8987a959c98f074706 -h r77rn.h.filess.io proj1_wishrocky`
		or (for newer versions)
		` mysql --ssl-mode=DISABLED   -u proj1_wishrocky -P 3306 -p94db734d1935c57ac05eab8987a959c98f074706 -h r77rn.h.filess.io proj1_wishrocky`
    
  
    
    To get list of database:
    
    `show databases;`
	
	To create database 
	```sql
	 drop database if exists database_name; 
	 create database database_name; 
	 ```
    
    To load database
    
    `use hospitals;`
    
    hospitals here is name of database
    
    Once database is loaded, to get list of tables:
    
    `show tables;`
    
    To get schema of tables:
    
    `desc patients;` or `describe patients;`
    
    where patients is name of table
	
	- To create table 
	```sql
	 drop table if exists table_name; 
	 create table table_name(....); 
	 ```
    
    - Creating table
        
        ```sql
        create table project (
        	emp_id int not null,
            id int not null,
            name varchar(30),
            location varchar(40),
            primary key(emp_id)
        );
        ```
     -  Adding Auto increment
        - SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.
     
		```sql
		-- To let the AUTO_INCREMENT sequence start with another value, use the following SQL statement:
		ALTER TABLE Persons AUTO_INCREMENT=100; 
		
		alter table employee 
		modify emp_id int not null auto_increment;
		```  
- Change mysql password if forget
  - Stop mysql service
     `sudo systemctl stop mysql`
   - start it in safe mode
     `sudo mysqld_safe --skip-grant-tables --skip-networking`
  - Then in other terminal type
    `mysql -u root`
  - when in mysql shell	
    `FLUSH PRIVILEGES;`
  `ALTER USER 'root'@'localhost' IDENTIFIED BY 'new_password';`
  - close the terminal of the safe mode and start mysql service again
    `sudo systemctl start mysql`
- running sql script in mysql
  `mysql -u username -p`
  then
`SOURCE /path/to/your/script.sql;`
Alternatively, you can execute the script directly from the command line without entering the MySQL shell
`mysql -u username -p < /path/to/your/script.sql`
- if else use in mysql 
  ```sql
  SET @primaryKeyValue = 13; /* Your primary key value here */

	IF EXISTS (SELECT 1 FROM TableB WHERE foreignKeyColumn = @primaryKeyValue) THEN
		-- Update the record in TableA
		UPDATE TableA
		SET someField = 'newValue' -- Set your field and value accordingly
		WHERE primaryKeyColumn = @primaryKeyValue;
	ELSE
		-- Delete the record in TableA
		DELETE FROM TableA
		WHERE primaryKeyColumn = @primaryKeyValue;
	END IF;

  ```
- creating and using procedures
  ```sql
	 -- to replace semicolon with // for procedures
	DELIMITER //

	CREATE PROCEDURE if not EXISTS UpdateOrDeleteQuestion(IN primaryKeyValue INT)
	BEGIN
		IF EXISTS (SELECT 1 FROM quiz_questions WHERE questionID = primaryKeyValue) THEN
			-- Update the record in questions
			UPDATE questions
			SET isDeleted = TRUE
			WHERE id = primaryKeyValue;
		ELSE
			-- Delete the record in questions
			DELETE FROM questions
			WHERE id = primaryKeyValue;
		END IF;
	END //

	DELIMITER ;

	-- Now you can call the procedure with the primary key value
	CALL UpdateOrDeleteQuestion(2);
	-- to delete it
	drop procedure UpdateOrDeleteQuestion;
  ```
 
- to run mysql in docker first setup `/var/lib/mysql` by
  `mysql_install_db --user=root --basedir=/usr --datadir=/var/lib/mysql`
  then
  ```bash
	mysqld_safe --user=root  &

	# Wait for MySQL to initialize (this is important)
	sleep 5
	
	# other scripts to start (like backend services)
	# npm start
  ```
  in order to check if mysql is listening on localhost:3306 try this
  `netstat -tuln | grep 3306`
  


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