In this post, I am sharing an advanced SQL Query to find a Permutations and Combinations of given string data of the table. The question is look like very complex query, but the solution is very simple.

You can apply self-joins and can prepare all available combinations. The T-SQL or Database Developer can practice this query before an interview.

Create a table with sample data:

CREATE TABLE tbl_StringAllCombinations (ID INT,TextData CHAR(1))
GO

INSERT INTO  tbl_StringAllCombinations VALUES 
(1,'A')
,(2,'B')
,(3,'C')
,(4,'D')
GO

The Solution: (This is my work around solution, Interviewer may ask for any other alternative solution so please also try to prepare it and share your comments…)

SELECT a.TextData, b.TextData, c.TextData, d.TextData
FROM tbl_StringAllCombinations a
join tbl_StringAllCombinations b on b.TextData not in (a.TextData)
join tbl_StringAllCombinations c on c.TextData not in (a.TextData, b.TextData)
join tbl_StringAllCombinations d on d.TextData not in (a.TextData, b.TextData, c.TextData)
order by 1, 2, 3, 4

The Result:

TextData TextData TextData TextData
-------- -------- -------- --------
A        B        C        D
A        B        D        C
A        C        B        D
A        C        D        B
A        D        B        C
A        D        C        B
B        A        C        D
B        A        D        C
B        C        A        D
B        C        D        A
B        D        A        C
B        D        C        A
C        A        B        D
C        A        D        B
C        B        A        D
C        B        D        A
C        D        A        B
C        D        B        A
D        A        B        C
D        A        C        B
D        B        A        C
D        B        C        A
D        C        A        B
D        C        B        A
(24 row(s) affected)