What does a foreign key constraint mean in SQL?

A foreign key constraint ensures that the values in one table match with the primary key values in another table. For example, consider an employee table containing employee details such as employee name, salary, department and so on. A foreign key constraint can be defined on this table to employee id where employee id is primary key in another employee details table.

What is a foreign key constraint in MySQL?

A foreign key constraint is a type of index that is used to restrict the referencing table to contain only valid values. We also call it a referential integrity constraint. This constraint is enforced automatically in MySQL whenever you insert new rows in the referencing table. Thus, if you insert a row in the parent table that refers to an invalid value in the child table, MySQL will return an error.

What does a foreign key constraint mean in MS SQL?

A foreign key is a database concept that ensures the relationship between two tables is one to many and can be used for data integrity. When you define a foreign key in a table, you are linking that table to another table that has the primary key as a foreign key. The foreign key acts as an index to the table it is linked to. Data consistency is maintained, as the primary key cannot exist without the foreign key.

What does a foreign key column mean in SQL?

A foreign key column is a column in a table that consists of the primary key of another table. The foreign key column can be referred to as the child table’s primary key. This relationship between two tables is called a one-to-one relationship when there is only one child table. When you specify a foreign key column, it means that the value of that column in the child table must match the primary key value in the parent table. The foreign key constraint prevents the parent table from

What is a foreign key constraint in SQL?

A foreign key constraint defines a relationship between two tables. It ensures that the values in one column of one table are unique within that column of another table. Thus, the idea of a foreign key is that, if you have two tables: table1 and table2, each of the column in table1 must have a unique value for each column in table2 and vice versa.