Skip to main content

What is a foreign key? Write a query to implement the same in MySQL.

 A foreign key is used to connect two tables. A FOREIGN KEY is a field (or assortment of it) in one table that alludes to the PRIMARY KEY in another table. The FOREIGN KEY requirement is utilised to forestall activities that would crush joins between tables.

To assign a foreign key, it is important to mention it while creating the table. It can be assigned by invoking the FOREIGN KEY query. Something like this:

FOREIGN KEY (Any_ID) REFERENCES Table_to_reference(Any_ID)

Labels:

Comments

Post a Comment

Popular Posts

How to find out Max Salary from each department

You can find maximum salary for each department by grouping all records by DeptId and then using MAX() function to calculate maximum salary in each group or each department. SQL Query: SELECT DeptID, MAX(Salary) FROM Employee  GROUP BY DeptID. This questions become more interesting if Interviewer will ask you to print department name instead of department id, in that case you need to join Employee table with Department using foreign key DeptID, make sure you do LEFT or RIGHT OUTER JOIN to include departments without any employee as well.  Here is the query
Post a Comment
Read more