SELECT SQL Matching Number - sql

Question

I have millions of rows of data that have similar values ​​like this:
Id Reff Amount
1 a1 1000
2 a2 -1000
3 a3 -2500
4 a4 -1500
5 a5 1500
every data must have positive and negative values. the question is, how do I show only records that don't have a similar value? like a row Id 3. thanks for help

Answer 1

You can use not exists:
select t.*
from mytable t
where not exists (select 1 from mytable t1 where t1.amount = -1 * t.amount)
A left join antipattern would also get the job done:
select t.*
from mytable t
left join mytable t1 on t1.amount = -1 * t.amount
where t1.id is null
Demo on DB Fiddle:
Id | Reff | Amount
-: | :--- | -----:
3 | a3 | -2500

Answer 2

SQL Fiddle
MS SQL Server 2017 Schema Setup:
CREATE TABLE Test(
Id int
,Reff varchar(2)
,Amount int
);
INSERT INTO Test(Id,Reff,Amount) VALUES (1,'a1',1000);
INSERT INTO Test(Id,Reff,Amount) VALUES (2,'a2',-1000);
INSERT INTO Test(Id,Reff,Amount) VALUES (3,'a3',-2500);
INSERT INTO Test(Id,Reff,Amount) VALUES (4,'a4',-1500);
INSERT INTO Test(Id,Reff,Amount) VALUES (5,'a5',1500);
Query 1:
select t.*
from Test t
left join Test t1 on t1.amount =ABS(t.amount)
where t1.id is null
Results:
| Id | Reff | Amount |
|----|------|--------|
| 3 | a3 | -2500 |

Answer 3

Using a NOT EXISTS or a LEFT JOIN will work fine to find the amounts that don't have an opposite amount in the data.
But to really find the amounts that don't balance out with an Amount sorted by ID?
For such SQL puzzle it should be handled as a Gaps-And-Islands problem.
So the solution might appear a bit more complicated, but it's actually quite simple.
It first calculates a ranking per absolute value.
And based on that ranking it filters the last amount where the SUM per ranking isn't balanced out (not 0)
SELECT Id, Reff, Amount
FROM
(
SELECT *,
SUM(Amount) OVER (PARTITION BY Rnk) AS SumAmountByRank,
ROW_NUMBER() OVER (PARTITION BY Rnk ORDER BY Id DESC) AS Rn
FROM
(
SELECT Id, Reff, Amount,
ROW_NUMBER() OVER (ORDER BY Id) - ROW_NUMBER() OVER (PARTITION BY ABS(Amount) ORDER BY Id) AS Rnk
FROM YourTable
) AS q1
) AS q2
WHERE SumAmountByRank != 0
AND Rn = 1
ORDER BY Id;
A test on rextester here
If the sequence doesn't matter, and just the balance matters?
Then the query can be simplified.
SELECT Id, Reff, Amount
FROM
(
SELECT Id, Reff, Amount,
SUM(Amount) OVER (PARTITION BY ABS(Amount)) AS SumByAbsAmount,
ROW_NUMBER() OVER (PARTITION BY ABS(Amount) ORDER BY Id DESC) AS Rn
FROM YourTable
) AS q
WHERE SumByAbsAmount != 0
AND Rn = 1
ORDER BY Id;