Hence, we can conclude that the relation between the person and employee tables is distinct to various i.e.An employee profile will not be existent lacking a person. However, every employee profile belongs to just one single person in the table relation. In the MySQL database structure model, each person occupies either single or multiple employee profiles. Supposing we have created two MySQL tables person(ID, Name, Address) and Employee(EmpID, ID, Profile, Contact).In MySQL, the parent table comprises the original key values in a table whereas the child table is defined as the linked table that refers to the main key values in the parental table in a database.CASCADE: It denotes that when the parent data is affected then, the child data is also altered accordingly since it is used in aggregation to ON DELETE or ON UPDATE.ON DELETE CASCADE: This MySQL Keyword is responsible to make changes on the child table when the parent table is affected.Col1_Parent,….,ColN_Parent: These are the parent table columns which holds Primary keys to which the foreign key will be associated.ParentTable_Name: This is the name of the parent table to be used in the query statement whose primary keys are linked to being used in the child table.Col1_Child,…,ColN_Child: These are the columns of the child table which has reference to Primary key in the parental table.It has a default value as NULL when we do not provide any data type but we need to add some data type for the proper execution of query either NULL or NOT NULL. Col1.,ColN: These are the column names that we want to create with the respective data type in the table.ChildTable_Name: It denotes the name of the child table related to the parent table.A foreign key for a MySQL ON DELETE CASCADE can be generated with the help of either using MySQL CREATE TABLE or MySQL ALTER TABLE statements.Here, the terms used are explained below: REFERENCES ParentTable_Name (Col1_Parent, …., ColN_Parent) We use the following syntax for the MySQL ON DELETE CASCADEfor foreign key using CREATE TABLE:ĬREATE TABLE ChildTable_Name(Col1 Data_Type. It means that if we delete any data or column values in the parental table then, with referential action the related data or column values with a foreign key in the sub-table will also be removed spontaneously. Hadoop, Data Science, Statistics & others
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