SQL Subquery with a single table result with NULL - sql

Question

I have tried to select with sub queries in only a single table. but for some reason i got a NULL result.
The table I have look like this.
| id | ItemCode | ItemAmount | Counter |
-----------------------------------------
| 1 | 001 | 1 | Counter-1 |
| 2 | 001 | 1 | Counter-2 |
| 3 | 002 | 2 | Counter-1 |
| 4 | 002 | 2 | Counter-2 |
| 5 | 002 | 1 | Counter-2 |
I have tried this SQL :
select
id,
itemCode,
(select ItemAmount where Counter = 'Counter-1') as 'Count 1 Result',
(select Counter where Counter = 'COUNTER-1') as 'Count Is 1',
(select ItemAmount where Counter = 'Counter-2') as 'Count 2 Result',
(select Counter where Counter = 'COUNTER-2') as 'Count Is 2',
from
My_Table
and the result I got is :
| id | ItemCode | Count 1 Result | Count Is 1 | Count 2 Result | Count Is 2 |
----------------------------------------------------------------------
| 1 | 001 | 1 | Counter-1 | NULL | NULL |
| 2 | 001 | NULL | NULL | 1 | Counter-2 |
| 3 | 002 | 2 | Counter-1 | NULL | NULL |
| 4 | 002 | NULL | NULL | 2 | Counter-2 |
| 5 | 002 | NULL | NULL | 1 | Counter-2 |
As you can see, i got NULL result with the NULL Value. How can i do it with the result like this :
| id | ItemCode | Count 1 Result | Count Is 1 | Count 2 Result | Count Is 2 |
-------------------------------------------------------------------------
| 1 | 001 | 1 | Counter-1 | 2 | Counter-2 |
--------------------------------------------------------------------------
| 2 | 002 | 2 | Counter-1 | 3 | Counter-2 |
--------------------------------------------------------------------------
I want to make it no NULL value anymore and there is no double Item Code with the SUM Item Amount if the counter and item code is have the same value.
Is that even possible to do it with one table ? if it is how do i do that. thanks in advance

Answer 1

Try conditional aggregation, something like:
SELECT min(id) id,
itemcode,
sum(CASE
WHEN counter = 'Counter-1' THEN
itemamount
ELSE
0
END) count1result,
'Counter-1' countis1,
sum(CASE
WHEN counter = 'Counter-2' THEN
itemamount
ELSE
0
END) count2result,
'Counter-2' countis2
FROM my_table
GROUP BY itemcode;

Answer 2

You can try to use Aggregate function condition to make it.
Here is SQL-server sample:
CREATE TABLE My_Table(
id INT,
ItemCode VARCHAR(50),
ItemAmount INT,
Counter VARCHAR(50)
);
INSERT INTO My_Table VALUES (1, '001', 1 ,'Counter-1');
INSERT INTO My_Table VALUES (2, '001', 1 ,'Counter-2');
INSERT INTO My_Table VALUES (3, '002', 2 ,'Counter-1');
INSERT INTO My_Table VALUES (4, '002', 2 ,'Counter-2');
INSERT INTO My_Table VALUES (5, '002', 1 ,'Counter-2');
Query 1:
select
ROW_NUMBER() OVER(ORDER BY itemCode) id,
itemCode,
SUM(CASE WHEN Counter = 'Counter-1' THEN ItemAmount ELSE 0 END) as 'Count 1 Result',
MAX(CASE WHEN Counter = 'COUNTER-1' THEN Counter END) as 'Count Is 1',
SUM(CASE WHEN Counter = 'Counter-2' THEN ItemAmount ELSE 0 END) as 'Count 2 Result',
MAX(CASE WHEN Counter = 'COUNTER-2' THEN Counter END) as 'Count Is 2'
from
My_Table
GROUP BY
itemCode
Results:
| id | itemCode | Count 1 Result | Count Is 1 | Count 2 Result | Count Is 2 |
|----|----------|----------------|------------|----------------|------------|
| 1 | 001 | 1 | Counter-1 | 1 | Counter-2 |
| 2 | 002 | 2 | Counter-1 | 3 | Counter-2 |

Answer 3

Even though I'm not sure what you are expecting with out disturbing your code I have given the query. Implement in your requirement
;WITH CTE AS (select
itemCode,
(select SUM(ItemAmount) where Counter = 'Counter-1') as 'Count 1 Result',
(select MAX(Counter) where Counter = 'COUNTER-1') as 'Count Is 1',
(select SUM(ItemAmount) where Counter = 'Counter-2') as 'Count 2 Result',
(select MAX(Counter) where Counter = 'COUNTER-2') as 'Count Is 2'
from
My_table
GROUP BY
itemCode,Counter )
Select RANK()OVER ( ORDER BY itemcode)Id,
itemCode,
MAX([Count 1 Result])[Count 1 Result],
MAX([Count Is 1])[Count Is 1],
MAX([Count 2 Result])[Count 2 Result],
MAX([Count Is 2])[Count Is 2]
from CTE
GROUP BY itemCode

Answer 4

For the data retrieval part the following would give your data,
by grouping on ItemCode and Counter:
select
ItemCode,
Counter,
min(Id) as Id,
sum(ItemAmount) as ItemAmount,
from
My_Table
group by ItemCode, Counter
ItemCode Counter Id ItemAmount
======== ========= === ==========
001 Counter-1 1 1
001 Counter-2 1 2
002 Counter-1 3 1
002 Counter-2 3 3
To display that as so called pivot table, rows-to-columns, there are several solutions, one generic SQL solution:
In Modern SQL:
select ItemCode,
ItemAmount filter (where Counter = 'Counter-1') as A1,
ItemAmount filter (where Counter = 'Counter-2') as A2
from (select
ItemCode,
Counter,
min(Id) as Id,
sum(ItemAmount) as ItemAmount,
from
My_Table
group by ItemCode, Counter)
group by ItemCode
If filter is still not supported in the used SQL:
select ItemCode,
sum(case when Counter = 'Counter-1' then ItemAmount end) as A1,
sum(case when Counter = 'Counter-2' then ItemAmount end) as A2,