ISRO2020-51

Question

The SQL query

SELECT columns
FROM TableA
RIGHT OUTER JOIN TableB
ON A.columnName = B.columnName
WHERE A.columnName IS NULL

returns the following:

• A. All rows in Table $\text{B}$, which meets equality condition above and, none from Table $\text{A}$ which meets the condition.
• B. All rows in Table $\text{A}$, which meets equality condition above and none from Table $\text{B}$, which meets the condition.
• C. All rows in Table $\text{B}$, which meets the equality condition
• D. All rows in Table $\text{A}$, which meets the equality condition

Comments

Not sure maybe option a).

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None are correct.

Answer 1

None of the above options

Explanation:

SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees
ON Orders.EmployeeID = Employees.EmployeeID;

This gave the result which is same as option A

but when I executed

SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees
ON Orders.EmployeeID = Employees.EmployeeID
where Orders.EmployeeID is NULL;

Result had only the records where OrderID was NULL

One can try it on w3schools to get a better understanding.

Also one can refer the following link to get a clear understanding

https://www.dofactory.com/sql/right-outer-join

Comments

You are correct. Please raise objection to this question.

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yes this in this question none of the option is matching

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It should return, all rows from table B which doesn't satisfy the equality condition & none from table A.

after joining, the table should be like this - 

A1	A2	B1	B2
meets condition	meets condition	meets condition	meets condition
meets condition	meets condition	meets condition	meets condition
NULL	NULL	can't meet	can't meet

according to given query only last row should be output.

Answer 2

Answer (a)

SELECT columns
FROM TableA
RIGHT OUTER JOIN TableB
ON A.columnName = B.columnName
WHERE A.columnName IS NULL

Query returns records of table B which meets equality condition. Thus option (a) matching.

Answer 3

option A. all rows from  table B which meets the condition and none from A which MEETS THE CONDITION.

Answer 4

(1) We are first doing A outer join B in this process all the rows of B which are failed to match with Any row of A(on given col.) are also included in result where All A’s columns are set to NULL

(2) Now we are imposing condition on A by  comparing colName to Null  So we are getting all rows where A.colName = null which are noting but all B table’s row which are failed to match with any row of A 

So this will fetch all rows where B is not matching with any row of A (on given Column)

which does not match with any option