Question

I’m a beginner in SQL and I have the following problem in SQL.

I need an SQL query that would calculate the difference between two continuous rows having the same value in field [idpersone] and regroupe them into a single row.

For example I need to transform my table to the desired data as shown below:

Table data:
idLigne | idperson | statut
--------|----------|-------
   L1         1         A
   L2         1         B
   L3         1         A
   L4         1         B
   L5         2         A
   L6         2         B
   L7         3         A
   L8         3         B

Desired output: 
idLigne | idpersonne | firstLighe | secondLigne
--------|------------|------------|------------
 L2-L1         1           L1           L2
 L4-L3         1           L3           L4
 L6-L5         2           L5           L6
 L8-L7         2           L7           L8

Answer 1

You might try something like this:

DECLARE @MyTable TABLE(idLigne VARCHAR(2), idperson INT, statut CHAR(1));

INSERT INTO @MyTable VALUES ('L1',1,'A')
, ('L2',1,'B')
, ('L3',1,'A')
, ('L4',1,'B')
, ('L5',2,'A')
, ('L6',2,'B')
, ('L7',3,'A')
, ('L8',3,'B')

; WITH a AS (
    SELECT idLigne=t2.idLigne+'-'+t1.idLigne
    , idpersonne=t1.idperson
    , firstLigne=t1.idLigne
    , secondLigne=t2.idLigne
    , r1=ROW_NUMBER()OVER(PARTITION BY t1.idLigne ORDER BY t2.idLigne)
    , r2=ROW_NUMBER()OVER(PARTITION BY t2.idLigne ORDER BY t1.idLigne)
    FROM @MyTable t1
    INNER JOIN @MyTable t2 ON t1.idperson=t2.idperson AND t1.statut='A' AND t2.statut='B'
)
SELECT idLigne
    , idpersonne
    , firstLigne
    , secondLigne
FROM a WHERE r1=r2
GO

Result: