SQL - Revert appended rows queried from Database table - sql

Question

I am trying to reverse or somehow pivot appended rows from a table through an SQL Query. The following example illustrates the table structure I have
Timestamp
ID
Value
2023-01-18
A
10
2023-01-19
A
15
2023-01-20
A
20
2023-01-18
B
10
2023-01-19
B
15
2023-01-20
B
20
2023-01-18
C
10
2023-01-19
C
15
2023-01-20
C
20
And I am trying to modify the query to pivot or group the rows equivalent to the following:
Timestamp
A
B
C
2023-01-18
10
10
10
2023-01-19
15
15
15
2023-01-20
20
20
20
What would be a solution for this query?
I have tried pivoting the query like the following which according to my research should do what I am hoping for, but maybe I am missing something as it returns an error message below.
SELECT Facility,
Site,
SUBSTRING(Name,
CHARINDEX('_',Name)+1,
( ((LEN(Name)) - CHARINDEX('_', REVERSE(Name)))
- CHARINDEX('_',Name) )
) AS Panel,
dateadd(hh,-7,TimestampUTC) as TimeStamp,
ActualValue
FROM PSS_KPIHistory
WHERE Name LIKE '%PercentLoopsInNormal'
PIVOT(ActualValue for Panel in(select distinct Panel from PSS_KPIHistory))
The above query returns columns Facility, Site, an extracted string from the column "Name" stored as new Column "Panel", a Timestamp and the Value (ActualValue). I am returning everything from the table that contains "PercentLoopsInNormal" in the "Name" Column. This returns the following error:
Message=Incorrect syntax near the keyword 'PIVOT'.
Incorrect syntax near ')'.

Answer 1

your data doesn't fit your wanted result, changing it you can do
you would need a dynamic approach to the problem
CREATE TABLE table1
([Timestamp] DATE, [ID] varchar(1), [Value] int)
;
INSERT INTO table1
([Timestamp], [ID], [Value])
VALUES
('2023-01-18', 'A', 10),
('2023-01-19', 'A', 15),
('2023-01-20', 'A', 20),
('2023-01-18', 'B', 10),
('2023-01-19', 'B', 15),
('2023-01-20', 'B', 20),
('2023-01-18', 'C', 10),
('2023-01-19', 'C', 15),
('2023-01-20', 'C', 20)
;
9 rows affected
DECLARE
#columns NVARCHAR(MAX) = '',
#sql NVARCHAR(MAX) = '';
-- select the Distinct ID
SELECT
#columns+=QUOTENAME( [ID]) + ','
FROM
(SELECT DISTINCT [ID] FROM table1) t1
ORDER BY
[ID];
-- remove the last comma
SET #columns = LEFT(#columns, LEN(#columns) - 1);
-- construct dynamic SQL
SET #sql ='
SELECT * FROM
(
SELECT
[Timestamp], [ID], [Value]
FROM
table1
) t
PIVOT(
MAX([Value])
FOR [ID] IN ('+ #columns +')
) AS pivot_table;';
--SELECT #sql
-- execute the dynamic SQL
EXECUTE sp_executesql #sql;
Timestamp
A
B
C
2023-01-18
10
10
10
2023-01-19
15
15
15
2023-01-20
20
20
20
fiddle

Answer 2

Here's the traditional pivot approach:
Step 1: identifying values from a single column that should be split in different columns (your discriminatory values are 'A', 'B' and 'C')
Step 2: aggregating on the field for which specific value you want one record only in the output, in this case [Timestamp]
SELECT [Timestamp],
MAX(CASE WHEN [ID] = 'A' THEN [Value] END) AS A,
MAX(CASE WHEN [ID] = 'B' THEN [Value] END) AS B,
MAX(CASE WHEN [ID] = 'C' THEN [Value] END) AS C
FROM tab
GROUP BY [Timestamp]
Typically Step1 requires the use of a window function, but in this case your [ID] field is ready to be used by Step2.
Check the demo here.