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SQL PUZZLE | The OUTPUT Puzzles – II | SQL Interview QUESTION

In this post you have to go through the sample data given below and answer the questions below. There are two tables called Employee and Department. Please check their definitions with data.

Sample Data for Puzzles

--

CREATE TABLE Employee
(
	 EmpID INT
	,EmpName VARCHAR(10)
	,DeptId INT
)
GO

INSERT INTO Employee VALUES
(1,'Pawan',1),
(1,'Pawan',2),
(2,'Avtaar',1)
GO

CREATE TABLE Department
(
	 DeptId INT
	,DeptName VARCHAR(20)
)
GO

--

Puzzle

Puzzle 1 : What is the OUTPUT of below query?

--

SELECT Employee.* FROM Employee, Department

--

OUTPUT

--


EmpID       EmpName    DeptId
----------- ---------- -----------

(0 rows affected)


--

Notes – Here we get 0 rows. Since here we will have Cartesian
product(Multiplication). —And one table –has 0 rows so we will get 0 rows as
the output

Puzzle 2 : What is the OUTPUT of below query?

--

SELECT EmpId FROM Employee
UNION 
SELECT DeptId FROM Department

--

OUTPUT

--

EmpId
-----------
1
2

(2 rows affected)

--

Notes – Here we will get 2 records 1 and 2. Note that it will get distinct
records from Emp table and dept table. Note if you have duplicate records in one
table also, UNION will make distinct from that table also. 🙂

Pawan Khowal

Pawan is a SQL Server Developer. If you need any help in writing code/puzzle or training please email at – pawankkmr”AT”gmail.com. Meanwhile please go throgh the top pages from his blog.

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