Question

which type of inner join fetches result with redundant data??

Answer 1

Let's represent two tables by two sets A and B.

If we talk about inner join then it contains the results of A ∩ B.
Equi Join is a type of inner join which gives redundant data.

Let's understand by an example.

Let there be two tables:
Customer(CustID, CustName)  and  Order(CustID, date, amount)

Equi join is done in the following way:
SELECT * 
FROM Customer JOIN Order
ON Customer.CustID = Order.CustID

This will result in a table with columns (CustID, CustName, CustID, date, amount)

In the result, CustID appears twice and it will contain identical data. Hence the result has redundant data.

There is one more inner join called NATURAL JOIN, which doesn't contain this redundancy in its results.

Answer 2

This can be represented by two tables by two sets A and B.

On the off chance that we discuss inward join then it contains the consequences of A and B.

Equi Join is a kind of inward join which gives redundant information.

How about we comprehend by an illustration.

May there be two tables:

Customer(CustID, CustName) and Order(CustID, date, sum)

Equi join is done in the following way:

SELECT *

FROM Customer JOIN Order

ON Customer.CustID = Order.CustID

This will bring about a table with columns (CustID, CustName, CustID, date, amount)

In the outcome, CustID shows up twice and it will contain indistinguishable information. Subsequently, the outcome has redundant information.

There is one more internal join called NATURAL JOIN, which doesn't contain this redundancy in its outcomes.