SQL Server 2017

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CREATE TABLE TSCHEDDOW (SysNr int,
                        DoWC int,
                        WorkStart time,
                        WorkEnd time,
                        ContractHours int)
INSERT INTO TSCHEDDOW
VALUES(24,1,'12:00','8:00',8),
      (25,2,'12:00','8:00',8),
      (26,2,'9:00','6:00',8),
      (27,5,'7:00','3:00',8);
      
SELECT *
FROM TSCHEDDOW;


SysNr
DoWC
WorkStart
WorkEnd
ContractHours


24
1
12:00:00
08:00:00
8

25
2
12:00:00
08:00:00
8

26
2
09:00:00
06:00:00
8

27
5
07:00:00
03:00:00
8


CREATE TABLE #temp (oldSysNr int,newSysNr int)
INSERT INTO #temp
VALUES(24,54),
      (25,55),
      (26,56),
      (27,57);

UPDATE TS
SET SysNr = T.newSysNr
FROM TSCHEDDOW TS
     JOIN #temp T ON TS.SysNr = T.oldSysNr
8 rows affected

SELECT *
FROM TSCHEDDOW;


SysNr
DoWC
WorkStart
WorkEnd
ContractHours


54
1
12:00:00
08:00:00
8

55
2
12:00:00
08:00:00
8

56
2
09:00:00
06:00:00
8

57
5
07:00:00
03:00:00
8

SysNr	DoWC	WorkStart	WorkEnd	ContractHours
24	1	12:00:00	08:00:00	8
25	2	12:00:00	08:00:00	8
26	2	09:00:00	06:00:00	8
27	5	07:00:00	03:00:00	8