SQL PUZZLE | Remove ALL if Others are Present Puzzle | SQL Interview Question

In this puzzle you have to get rows with the following conditions-

1 : If any Id has 1 row with All in the dat column that row should come.
2 : If any Id has multiple rows and one of the row has All in the dat column then the row with the All column should not come.

For more details please refer sample input and expected output.

Sample Input

Id Val Dat
1 a Simple
1 a All
1 a Double
2 b Triple
2 b All
3 c All
3 c Simple
3 c Double
4 e All
5 f All

Expected output

Id Val Dat
1 a Simple
1 a Double
2 b Triple
3 c Simple
3 c Double
4 e All
5 f All

Script – DDL and INSERT sample data

 ```-- CREATE TABLE MyData ( Id INT ,Val VARCHAR(10) ,Dat VARCHAR(20) ) GO INSERT INTO MyData VALUES (1,'a','Simple'), (1,'a','All'), (1,'a','Double'), (2,'b','Triple'), (2,'b','All'), (3,'c','All'), (3,'c','Simple'), (3,'c','Double'), (4,'e','All'), (5,'f','All') GO SELECT * FROM MyData GO -- ```

SOLUTION 1 – USING PARTITION COUNT, CASE and CASE

 ```-- SELECT Id,Val,Dat FROM ( SELECT * , COUNT(1) OVER (PARTITION BY Id ORDER BY Id) a , CASE WHEN Dat = 'All' THEN 1 ELSE 0 END b FROM MyData )k WHERE 1 = CASE WHEN a = 1 AND b = 1 THEN 1 WHEN a > 1 AND b = 0 THEN 1 ELSE 0 END GO -- ```

OUTPUT 1

 ```-- Id Val Dat ----------- ---------- -------------------- 1 a Simple 1 a Double 2 b Triple 3 c Simple 3 c Double 4 e All 5 f All (7 rows affected) -- ```

SOLUTION 2 – USING PARTITION COUNT, CASE and OR

 ```-- SELECT Id,Val,Dat FROM ( SELECT * , COUNT(1) OVER (PARTITION BY Id ORDER BY Id) a , CASE WHEN Dat = 'All' THEN 1 ELSE 0 END b FROM MyData )k WHERE k.a = 1 OR ( k.b = 0 AND k.a > 1 ) GO -- ```

OUTPUT 2

 ```-- Id Val Dat ----------- ---------- -------------------- 1 a Simple 1 a Double 2 b Triple 3 c Simple 3 c Double 4 e All 5 f All (7 rows affected) -- ```

SOLUTION 3 – Using Outer Apply and ISNULL

 ```-- SELECT k.Id,k.Val, ISNULL(n.Dat,'All') Dat FROM ( SELECT DISTINCT Id,Val FROM MyData )k OUTER APPLY ( SELECT Dat FROM MyData b WHERE Dat <> 'All' AND k.Id = b.Id AND b.Val = k.Val )n -- ```

OUTPUT 3

 ```-- Id Val Dat ----------- ---------- -------------------- 1 a Simple 1 a Double 2 b Triple 3 c Simple 3 c Double 4 e All 5 f All (7 rows affected) -- ```

SOLUTION 4 – Using UNION ALL and COUNT

 ```-- Select ID,Val,Dat FROM MyData Where Dat != 'All' UNION ALL SELECT ID,VAL,Max(dat) FROM MYData GROUP by ID,val having count(*) = 1 and MAX(dat) = 'All' -- ```

OUTPUT 4

 ```-- Id Val Dat ----------- ---------- -------------------- 1 a Simple 1 a Double 2 b Triple 3 c Simple 3 c Double 4 e All 5 f All (7 rows affected) -- ```

Enjoy 🙂

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.

Page Detail URL
☛ SQL Tricky Queries https://msbiskills.com/sql-puzzles-finding-outputs/
☛ SQL Server Perfomance tuning Articles https://msbiskills.com/sql-performance-tuning/
☛ SQL Server Articles https://msbiskills.com/t-sql/
☛ SQL Interview Questions & Answers https://msbiskills.com/sql-server-interview-questions/