How to find rows in ms-sql with another rows' value followingly? - sql-server

Question

I have created an Sql table to trace objects' operation history. I have two columns; first one is the self tracing code and second tracing code is the tracing code for the code coming from source object to target. I created this to be able to look up the route of operations through the objects. You can see the tracing sample table below:
I need to create an sql code to query to show all the route in one table. When I first select the self code, it will be the incoming code for previous rows. There may be more than one incoming code to self and I want to be able to trace all. And I want to reach end until my search is null.
I tried select query like below but I am so new sql and need your help.
SELECT [TracingCode.Self],
[TracingCode.Incoming],
[EquipmentNo]
FROM [MKP_PROCESS_PRODUCT_REPORTS].[dbo].[ProductionTracing.Main]
WHERE [TracingCode.Self] = (SELECT [TracingCode.Incoming]
FROM [MKP_PROCESS_PRODUCT_REPORTS].[dbo].[ProductionTracing.Main]
WHERE [TracingCode.Self] = (SELECT [TracingCode.Incoming]
FROM [MKP_PROCESS_PRODUCT_REPORTS].[dbo].[ProductionTracing.Main]
WHERE [TracingCode.Self] = (SELECT [TracingCode.Incoming]
FROM [MKP_PROCESS_PRODUCT_REPORTS].[dbo].[ProductionTracing.Main]
WHERE [TracingCode.Self] = '028.001.19.2.3')));

Answer 1

To do this kind of parent/child thing to any level without explicitly coding all levels you need to use a recursive CTE.
More details here
https://www.red-gate.com/simple-talk/sql/t-sql-programming/sql-server-cte-basics/
Here is some test data and a solution I came up with. Note that three records actually match 028.001.19.2.3
If this doesn't do what you need please explain further with sample data.
DECLARE #Sample TABLE (
TC_Self CHAR(14) NOT NULL,
TC_In CHAR(14) NOT NULL,
EquipmentNo INT NOT NULL
);
INSERT INTO #Sample (TC_Self, TC_In, EquipmentNo)
VALUES
('028.001.19.2.3','026.003.19.2.2',96),
('028.001.19.2.3','026.001.19.2.2',96),
('028.001.19.2.3','026.002.19.2.2',96),
('028.001.19.2.2','026.002.19.2.1',96),
('028.001.19.2.2','026.002.19.2.1',96),
('028.001.19.2.1','026.002.19.1.1',96),
('026.003.19.2.2','024.501.19.2.5',117),
('024.501.19.2.5','024.501.19.2.6',999),
('024.501.19.2.6','024.501.19.2.7',998);
WITH CTE (RecordType, TC_Self, TC_In, EquipmentNo)
AS
(
-- This is the 'root'
SELECT 'Root' RecordType, TC_Self, TC_In, EquipmentNo FROM #Sample
WHERE TC_Self = '028.001.19.2.3'
UNION ALL
SELECT 'Leaf' RecordType, S.TC_Self, S.TC_In, S.EquipmentNo FROM #Sample S
INNER JOIN CTE
ON S.TC_Self = CTE.TC_In
)
SELECT * FROM CTE;
Also please note that most of the time to generate this answer was taken in generating the sample data to use.
In future when asking questions, people are far more likely to help if you post this sample data generation yourself