SQL Puzzle | The Concatenation Puzzle | SQL Interview Question

In this puzzle you have to concat columns Nm and Val if they were not already concatenated at the beginning in Val column. For more details please see the sample input and expected output.

Sample Input

Id Nm Val
1 A 1
2 B 1
3 CC CC11
4 D 12
5 E E71
6 F F0

Expected Output

Id Nm Val NewVal
1 A 1 A1
2 B 1 B1
3 CC CC11 CC11
4 D 12 D12
5 E E71 E71
6 F F0 F0

Script – DDL and INSERT Sample Data

--

CREATE TABLE TheConcatPuzzle
(
	 Id INT
	,Nm VARCHAR(10)
	,Val VARCHAR(20)
)
GO

INSERT INTO TheConcatPuzzle VALUES
(1,'A','1'),
(2,'B','1'),
(3,'CC','CC11'),
(4,'D','12'),
(5,'E','E71'),
(6,'F','F0')
GO

SELECT * FROM TheConcatPuzzle
GO

--

SOLUTION – 1

--

SELECT *, IIF(CHARINDEX(Nm,Val)=0,CONCAT(Nm,Val),Val) NewVal FROM TheConcatPuzzle
GO

--

Output – 1

--

Id          Nm         Val                  NewVal
----------- ---------- -------------------- ------------------------------
1           A          1                    A1
2           B          1                    B1
3           CC         CC11                 CC11
4           D          12                   D12
5           E          E71                  E71
6           F          F0                   F0

(6 rows affected)


--

SOLUTION – 3

--

SELECT *,CASE WHEN SUBSTRING(val,1,LEN(nm)) = nm THEN val ELSE concat(nm,val) END NewVal
FROM TheConcatPuzzle

--

Output – 3

--

Id          Nm         Val                  NewVal
----------- ---------- -------------------- ------------------------------
1           A          1                    A1
2           B          1                    B1
3           CC         CC11                 CC11
4           D          12                   D12
5           E          E71                  E71
6           F          F0                   F0

(6 rows affected)


--

SOLUTION – 3

--

SELECT *, IIF(Val LIKE NM+'%',Val,CONCAT(Nm,Val)) NewVal
FROM TheConcatPuzzle

--

Output – 3

--

Id          Nm         Val                  NewVal
----------- ---------- -------------------- ------------------------------
1           A          1                    A1
2           B          1                    B1
3           CC         CC11                 CC11
4           D          12                   D12
5           E          E71                  E71
6           F          F0                   F0

(6 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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