Left join sql, database systems

What is left join?

Left join shows all rows from the left table and shows only matching rows from the right table.

RegistrationNoMarks
T4Tutorials177
T4Tutorials232

Table: Exams

Inner join shows results from both tables where there is any match between columns in both tables.

RegistrationNoFee
T4Tutorials11000
T4Tutorials22000
T4Tutorials33000

Table: Accounts

Now, we have two different tables. If we want to show the record of both tables in one single table then we can use a left join to join both two tables.

Query:

SELECT Exams.RegistrationNo, Exams.Marks, Accounts.Fee FROM Exams LEFT JOIN Accounts ON Exams.RegistrationNo =  Accounts.RegistrationNo

RegistrationNoMarksFee
T4Tutorials1771000
T4Tutorials2322000

Table: Table generated after Left Join

 

Test Your Understandings

1. Left join shows some rows from left table ? YES / NO

Answer - Click Here:
No, its show all rows

2. Left join shows all rows from Right table? YES / NO

Answer - Click Here:
No, it can only show matching rows from right table.

3. SELECT Exams.Marks, Accounts.Fee FROM Exams LEFT JOIN Accounts?

In this query, exams is the right table and accounts is the left the table.

Yes/No

Answer - Click Here:
No, exams is left table