Dependencies in DBMS is a relation between two or more attributes. It has the following types in DBMS −Functional DependencyFully-Functional DependencyTransitive DependencyMultivalued DependencyPartial DependencyLet us start with Functional Dependency −Functional DependencyIf the information stored in a table can uniquely determine another information in the same table, then it is called Functional Dependency. Consider it as an association between two attributes of the same relation.If P functionally determines Q, thenP -> QLet us see an example −EmpIDEmpNameEmpAgeE01Amit28E02Rohit31In the above table, EmpName is functionally dependent on EmpID because EmpName can take only one value for the given value of EmpID:EmpID -> EmpNameThe same is displayed ... Read More

Identifying entity relationships in DBMS is used to identify a relationship between strong and weak entity.Before beginning, let us take an example of Professor entity, which is our Strong Entity, with Professor_ID as a Primary Key −Professor_IDProfessor_NameProfessor_CityProfessor_SalaryThe weak entity is Professor_Dependents entity:NameDOBRelationNow, let us continue, Weak EntityWeak Entity is dependent on Strong Entity and does not have a primary key. Weak Entity has a partial key. It is represented as double rectangle −Strong EntityOther entities are dependent on Strong Entity and it has a key attribute i.e. a primary key and represented as a single rectangle.Identifying RelationshipsIt links the strong and weak entity ... Read More

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