SQL Server 2019

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28 rows affected

DECLARE @payload nvarchar(max)=N'[
   {
      "dow": 1,
      "T19_00": 10,
      "T19_30": 10,
      "T20_00": 10,
      "T20_30": 10
   },
   {
      "dow": 2,
      "T19_00": 20,
      "T19_30": 20,
      "T20_00": 20,
      "T20_30": 20
   },
   {
      "dow": 3,
      "T19_00": 20,
      "T19_30": 20,
      "T20_00": 20,
      "T20_30": 20
   },
   {
      "dow": 4,
      "T19_00": 20,
      "T19_30": 20,
      "T20_00": 20,
      "T20_30": 20
   },
   {
      "dow": 5,
      "T19_00": 20,
      "T19_30": 20,
      "T20_00": 20,
      "T20_30": 30
   },
   {
      "dow": 6,
      "T19_00": 20,
      "T19_30": 20,
      "T20_00": 20,
      "T20_30": 30
   },
   {
      "dow": 7,
      "T19_00": 20,
      "T19_30": 20,
      "T20_00": 20,
      "T20_30": 20
   }
]'

UPDATE WeeklySlots
SET slots = v.slots
FROM WeeklySlots ws
JOIN OPENJSON (@payload)
  WITH 
  (
    dow       int,
    T19_00    int,
    T19_30    int,
    T20_00    int,
    T20_30    int
  ) p
  CROSS APPLY (VALUES
      ('T19_00', p.T19_00),
      ('T19_00', p.T19_00),
      ('T19_00', p.T19_00),
      ('T19_00', p.T19_00)
  ) v(slotCode, slots)
  ON p.dow = ws.dow AND v.slotCode = ws.slotCode
;

SELECT * FROM WeeklySlots

dow	slots	SlotCode
1	10	T19_00
2	20	T19_00
3	20	T19_00
4	20	T19_00
5	20	T19_00
6	20	T19_00
7	20	T19_00
1	0	T19_30
2	20	T19_30
3	20	T19_30
4	20	T19_30
5	10	T19_30
6	10	T19_30
7	20	T19_30
1	0	T20_00
2	20	T20_00
3	20	T20_00
4	20	T20_00
5	10	T20_00
6	10	T20_00
7	20	T20_00
1	0	T20_30
2	20	T20_30
3	20	T20_30
4	20	T20_30
5	20	T20_30
6	20	T20_30
7	20	T20_30