HOW TO JOIN 3 OR MORE TABLES IN SQL | TWO WAYS

hello everyone in this video we are going to understand or how we can join three or more tables okay so before starting with the queries let's understand the basic structure of the three tables okay so I have three tables one is employees are there is details for this department so an employee's table we have employee ID and employee me ID and a name ER is a primary key and then there is another table details which has the foreign key ID okay so this idea basically is linked to this table okay so this is a foreign key then D ID which is a foreign key where the ID is also foreign key and salary salary okay so this is the details table and then there is one department table which gives the details for the department so as this will the foreign key D ID is a primary key in this table so di D D name and man basically Department ID Department name and manager of the department okay so these are the three tables and we are going to see two ways how we can join join the or attributes like he named all three manage all of these these attributes all of these together in one way how we can join these three tables so there are two ways so let's see the first way which is by using joints so in this we will simply select whatever we want to print so select a name D name man sad manager and Saturday okay then we write from employees E so we'll give analyze to this table employees E okay employees e inner join details D so we are joining these two tables and we are giving allies E and D to these two tables and when we write inner join we also have to write on on what common attribute okay so on a dot e ID is equal to d dot e ID so first we are joining these two tables then again we are writing no join department thought table and we're giving analyze to it so your I've given analyze DP okay and on um so you are we had your we are joining this in the stable so DP dot di D is equal to d dot di D so basically these two tables so this is how we join three tables okay so basically first we'll join these two tables on the common heart attribute e underscore ID and then we will join these two tables on the common attribute they underscore ID okay so this is how the three tables are going to be joined okay the second way is by using parent-child relationship this is very simple all you have to do is select whatever you want to print okay so en disco named Janos Connie mance and everything selected from employees e given a live stream price employee details D Department deeply okay allies we're simply that erode a ID is equal to D dot yeah it's the same thing a dot AI d is equal to d dot e ID so these two tables will be joined okay and D dot d ID is equal to DP by D so these two tables will be drawn so basically select whatever you want to print from the tables we're simply simply a foreign key of a table is equal to the primary key of the other table that is how both the that is how all the three tables are going to be joined okay so these are the two ways in which we can join three tables one is by using visuals are there is missing parent-child relationship I hope it is clear if this video helped you in any way do consider subscribing to the channel thank you

Channel: Crack Concepts

Views: 121,473

Rating: 4.9025607 out of 5

Keywords: Joins, Joins in sql, Sql, Sql interview questions and answers

Id: wdz4MRlzOyE

Length: 4min 4sec (244 seconds)

Published: Sun Oct 20 2019