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SQL PUZZLE | GET multiple Values or All Nulls ? SQL Interview Question

One of my dear friend(Vaibhav) asked this question to me today, So I thought of sharing it with you all guys. In the puzzle you have to find out rows here you have more than 1 value present in the columns(a,b,c). If all the columns have Nulls then that row should also be considered as part of output. Please check out sample input and expected output.

Sample Input

ID a b c
1 NULL NULL NULL
2 NULL NULL 10
3 NULL 10 NULL
4 20 NULL NULL
5 NULL 10 15
6 20 19 NULL

Expected output

Id a b c
1 NULL NULL NULL
5 NULL 10 15
6 20 19 NULL

Script – DDL and INSERT sample data

--

CREATE TABLE testMultiple
(
	ID INT
	,a INT
	,b INT
	,c INT
)
GO

INSERT INTO testMultiple VALUES
(1,NULL,NULL,NULL),
(2,NULL,NULL,10),
(3,NULL,10,NULL),
(4,20,NULL,NULL),
(5,NULL,10,15),
(6,20,19,NULL)
GO

SELECT * FROM testMultiple
GO


--

SOLUTION 1 | USING ISNULL & Coalesce

--

SELECT Id,a,b,c
FROM testMultiple
WHERE COALESCE(a, b , c) <> ISNULL(a,0)+ ISNULL(b,0)+ ISNULL(c,0)
or COALESCE(a, b , c) IS NULL

--

OUTPUT – 1

--

Id          a           b           c
----------- ----------- ----------- -----------
1           NULL        NULL        NULL
5           NULL        10          15
6           20          19          NULL

(3 rows affected)


--

SOLUTION 1 | USING IIF/CASE

--

SELECT Id,a,b,c
FROM testMultiple
WHERE IIF(a IS NULL,1,0)+IIF(b IS NULL,1,0)+IIF(c IS NULL,1,0)<> 2

--

OUTPUT – 2

--

Id          a           b           c
----------- ----------- ----------- -----------
1           NULL        NULL        NULL
5           NULL        10          15
6           20          19          NULL

(3 rows affected)


--

Enjoy 🙂

Please add comment(s) if you have one or multiple solutions in mind. Thank You.

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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