Suppose if a session is killed in the middle of a transaction then that current MySQL transaction will be rolled back by MySQL and ended. It means that all the database changes made in the current transaction will be removed. It is called n implicit rollback when the session is killed.ExampleSuppose we have the following values in the table ‘marks’mysql> Select * from marks; +------+---------+-----------+-------+ | Id   | Name    | Subject   | Marks | +------+---------+-----------+-------+ |    1 | Aarav   | Maths     |    50 | |    1 | Harshit | Maths   ... Read More

It can be understood with the help of the following example using the table named ‘Student’ having the following description −mysql> DESCRIBE Student; +--------+-------------+------+-----+---------+-------+ | Field  | Type        | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | Name   | varchar(20) | YES  |     | NULL    |       | | RollNo | int(11)     | YES  |     | NULL    |       | | Grade  | varchar(10) | YES  |     | NULL    |       | +--------+-------------+------+-----+---------+-------+ 3 rows in set ... Read More

MySQL always throws NULL as the result of arithmetic calculations in which one of the arguments is NULL. Consider the following example having NULL as an argument with addition, subtraction, multiplication, and division −mysql> Select 10*NULL; +---------+ | 10*NULL | +---------+ |    NULL | +---------+ 1 row in set (0.12 sec) mysql> Select 10+NULL; +---------+ | 10+NULL | +---------+ | NULL | +---------+ 1 row in set (0.00 sec) mysql> Select 10-NULL; +---------+ | 10-NULL | +---------+ |    NULL | +---------+ 1 row in set (0.07 sec) mysql> Select 10/NULL; +---------+ | 10/NULL | +---------+ ... Read More

As we know that built-in-commands (\G and \g) send the command to MySQL server for execution and with the help of Semicolon (;) MySQL determines the end of the statement. For using all three and getting the result without error, we need to write three queries, one query with \G, one with \g and other with a semicolon (;) in the end, in a single statement.Examplemysql> Select * from student\G select * from ratelist\g select NOW(); *************************** 1. row ***************************   Name: Gaurav RollNo: 100  Grade: B.tech *************************** 2. row ***************************   Name: Aarav RollNo: 150  Grade: M.SC *************************** 3. ... Read More

As we know that built-in-commands (\G and \g) send the command to MySQL server for execution and both of them have the different format of the result set. For combining them and getting the result without error, we need to write two queries, one query with \G and other with \g at the end, in a single statement.Examplemysql> Select * from student\G select * from ratelist\g *************************** 1. row ***************************   Name: Gaurav RollNo: 100  Grade: B.tech *************************** 2. row ***************************   Name: Aarav RollNo: 150  Grade: M.SC *************************** 3. row ***************************   Name: Aryan RollNo: 165  Grade: M.tech 3 ... Read More

As we know that built-in-commands (\G and \g) send the command to MySQL server for execution and with the help of Semicolon (;) MySQL determines the end of the statement. It is also known that both of them have different format of the result set. For combining them and getting the result without error, we need to write two queries, one query with either \G or \g and other with a semicolon (;) at the end, in a single statement.ExampleCombining \G and Semicolon (;) −mysql> Select * from student\G select * from ratelist; *************************** 1. row ***************************   Name: Gaurav ... Read More

As we know that \G option sends the command to MySQL server for execution and with the help of Semicolon (;) MySQL determines the end of the statement. It is also known that both of them have a different format of the result set.Now, if we will use both of those in MySQL statement then the output would be produced on the basis that which of them is encountered first by MySQL. For others, MySQL will produce an error. It can be understood with the help of the following example −mysql> Select CURDATE();\G +------------+ | CURDATE()  | +------------+ | 2017-11-06 ... Read More

We can use ROLLBACK command to eliminate the changes, made in a current transaction, permanently from MySQL database. Suppose if we run some DML statements and it updates some data objects, then ROLLBACK command will eliminate these updates permanently from the database. Example Suppose we have the following data in table ‘marks’ and we applied the transaction and ROLLBACK command as follows − mysql> SELECT * FROM Marks; +------+---------+---------+-------+ | Id | Name | Subject | Marks | +------+---------+---------+-------+ | 1 | Aarav | Maths | ... Read More

We can use COMMIT command to make the changes, made in a current transaction, permanently recorded in MySQL database. Suppose if we run some DML statements and it updates some data objects, then COMMIT command will record these updates permanently in the database.Examplemysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec) mysql> INSERT INTO Marks Values(1, 'Aarav', 'Maths', 50); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO Marks Values(2, 'Harshit', 'Maths', 55); Query OK, 1 row affected (0.00 sec) mysql> COMMIT; Query OK, 0 rows affected (0.06 sec)In this example, the COMMIT statement will ... Read More

We can run “SELECT @@AUTOCOMMIT” command to check the current transaction mode.mysql> Select @@AUTOCOMMIT; +--------------------+ | @@AUTOCOMMIT       | +--------------------+ |       1            | +--------------------+ 1 row in set (0.05 sec) mysql> SET AUTOCOMMIT = 0; Query OK, 0 rows affected (0.00 sec) mysql> Select @@AUTOCOMMIT; +--------------------+ | @@AUTOCOMMIT       | +--------------------+ |         0          | +--------------------+ 1 row in set (0.00 sec)