Entity in DBMS can be a real-world object with an existence, For example, in a Company database, the entities can be Employees, Department, Project, etc. In a College database, the entities are Profession, Students, Result, Activities, etc.An entity is represented as a single rectangle, shown belowThe following are the entity relationships −One-to-One RelationshipUnder One-to-One (1:1) relationship, an instance of entity P is related to instance of entity Q and an instance of entity Q is related to instance of entity P.Let us see an example −A person can have only one passport, and a passport is assigned to a single person.One-to-Many RelationshipUnder ... Read More

It is quite possible to add multiple virtual generated columns in a MySQL table. It can be illustrated with the following example as follows −Examplemysql> Create table profit(cost int, price int, profit int AS (price-cost), price_revised int AS (price-2)); Query OK, 0 rows affected (0.73 sec) mysql> Describe profit; +---------------+---------+------+-----+---------+-------------------+ | Field         | Type    | Null | Key | Default | Extra             | +---------------+---------+------+-----+---------+-------------------+ | cost          | int(11) | YES  |     | NULL    |               ... Read More

It is quite possible to add multiple stored generated columns in a MySQL table. It can be illustrated with the following example as follows −Examplemysql> Create table profit1(cost int, price int, profit int AS (price-cost) STORED, price_revised int AS (price-2) STORED); Query OK, 0 rows affected (0.36 sec) mysql> Describe profit1; +---------------+---------+------+-----+---------+------------------+ | Field         | Type    | Null | Key | Default | Extra            | +---------------+---------+------+-----+---------+------------------+ | cost          | int(11) | YES  |     | NULL    |             ... Read More

For adding MySQL stored GENERATED COLUMNS in a table, we can use the same syntax as adding a column just adding “AS(expression)” after the data type. Its syntax would be as follows −SyntaxALTER TABLE table_name ADD COLUMN column_name AS(expression)STORED;Examplemysql> ALTER TABLE employee_data_stored ADD COLUMN FULLName Varchar(200) AS (CONCAT_WS(" ", 'First_name', 'Last_name')) STORED; Query OK, 2 rows affected (1.23 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> Describe employee_data_stored; +------------+--------------+------+-----+---------+------------------+ | Field      | Type         | Null | Key | Default | Extra            | +------------+--------------+------+-----+---------+------------------+ | ID       ... Read More

Followings are some basic differences between MySQL stored GENERATED COLUMNS and MySQL virtual GENERATED COLUMNS −In terms of Disk SpaceIf we see the difference in terms of disk space then virtual generated columns would not take any disk space. On the other hand, the stored generated column would take disk space.In terms of operationIf we see the difference in terms of operation then virtual generated columns are INPLACE operations which means that the table definition is changed without having to recopy all the data again. On the other hand, stored generated columns are a copy operation and it has the ... Read More

It can be illustrated with the help of an example in which we are creating a stored generated column in the table named ‘employee_data_stored’. As we know that stored generated column can be generated by using the keyword ‘stored’.Examplemysql> Create table employee_data_stored(ID INT AUTO_INCREMENT PRIMARY KEY, First_name VARCHAR(50) NOT NULL, Last_name VARCHAR(50) NOT NULL, FULL_NAME VARCHAR(90) GENERATED ALWAYS AS(CONCAT(First_name, ' ', Last_name)) STORED); Query OK, 0 rows affected (0.52 sec) mysql> DESCRIBE employee_data_stored; +------------+-------------+------+-----+---------+------------------+ | Field      | Type        | Null | Key | Default | Extra            | +------------+-------------+------+-----+---------+------------------+ | ... Read More

For adding MySQL virtual GENERATED COLUMNS in a table, we can use the same syntax as adding a column just adding “AS(expression)” after the data type. Its syntax would be as follows −SyntaxALTER TABLE table_name ADD COLUMN column_name AS(expression);Examplemysql> ALTER TABLE employee_data ADD COLUMN FULLName Varchar(200) AS(CONCAT_WS(" ", 'First_name', 'Last_name')); Query OK, 0 rows affected (0.49 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> Describe employee_data; +------------+--------------+------+-----+---------+-------------------+ | Field      | Type         | Null | Key | Default | Extra             | +------------+--------------+------+-----+---------+-------------------+ | ID         ... Read More

It can be illustrated with the help of an example in which we are creating a stored generated column in the table named ‘triangle_stored’. As we know that stored generated column can be generated by using the keyword ‘stored’.Examplemysql> Create table triangle_stored(SideA DOUBLE, SideB DOUBLE, SideC DOUBLE AS (SQRT(SideA * SideB + SideB * SideB)) STORED); Query OK, 0 rows affected (0.47 sec) mysql> Describe triangle_stored; +-------+--------+------+-----+---------+------------------+ | Field | Type   | Null | Key | Default | Extra            | +-------+--------+------+-----+---------+------------------+ | SideA | double | YES  |     | NULL   ... Read More

It can be illustrated with the help of an example in which we are creating a virtual generated column in the table named ‘triangle’. As we know that virtual generated column can be generated with or without using the keyword ‘virtual’.Examplemysql> Create table triangle(SideA DOUBLE, SideB DOUBLE, SideC DOUBLE AS (SQRT(SideA * SideB + SideB * SideB))); Query OK, 0 rows affected (0.44 sec) mysql> Describe Triangle; +-------+--------+------+-----+---------+-------------------+ | Field | Type   | Null | Key | Default | Extra             | +-------+--------+------+-----+---------+-------------------+ | SideA | double | YES  |     | ... Read More

It can be illustrated with the help of an example in which we are creating a virtual generated column in the table named ‘employee_data’. As we know that virtual generated column can be generated with or without using the keyword ‘virtual’.Examplemysql> Create table employee_data(ID INT AUTO_INCREMENT PRIMARY KEY,        First_name VARCHAR(50) NOT NULL, Last_name VARCHAR(50) NOT NULL,        FULL_NAME VARCHAR(90) GENERATED ALWAYS AS(CONCAT(First_name, '', Last_name))); Query OK, 0 rows affected (0.55 sec) mysql> DESCRIBE employee_data; +------------+-------------+------+-----+---------+-------------------+ | Field      | Type        | Null | Key | Default | Extra     ... Read More