Simplyfing update query with case when - sql-server

Question

I have a query where there is a lot of repetitions of one condition. I am wondering - is it possible to put this condition into variable or something like that, so not the whole sentence is repeated each time?
The part which is repeating:
ISNULL((CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR
WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END),0)
In query it looks like this:
UPDATE #tblALL_HOURS SET REG_WORK_COST = (CASE WHEN MINUTE_FROM >= 0 AND MINUTE_FROM <= #6h AND MINUTE_TO >= #6h AND MINUTE_TO <= #18h
AND IS_ABSENT = 0
THEN (DATEDIFF(MINUTE, DATEADD(MINUTE, #6h, CAST(CAST(DATE_TO AS DATE) AS DATETIME)), date_to)/60.00) * (BRUTO_HOUR + ISNULL((CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END),0))
WHEN MINUTE_FROM >= 0 AND MINUTE_FROM <= #6h AND MINUTE_TO >= #18h AND MINUTE_TO < #24h
AND IS_ABSENT = 0
THEN 12.00 * (BRUTO_HOUR + ISNULL((CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END),0))
WHEN MINUTE_FROM >= #6h AND MINUTE_FROM <= #18h AND MINUTE_TO >= #6h AND MINUTE_TO <= #18h
AND IS_ABSENT = 0
THEN (DATEDIFF(MINUTE, DATE_FROM, DATE_TO) / 60.00) * (BRUTO_HOUR + ISNULL((CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END),0))
WHEN MINUTE_FROM >= #6h AND MINUTE_FROM <= #18h AND MINUTE_TO >= #18h AND MINUTE_TO < #24h
AND IS_ABSENT = 0
THEN (DATEDIFF(MINUTE, DATE_FROM, DATEADD(MINUTE, #18h, CAST(CAST(DATE_FROM AS DATE) AS DATETIME))) / 60.00) * (BRUTO_HOUR + ISNULL((CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END),0))
END)
Is it possible to have something like this instead:
WHEN MINUTE_FROM >= #6h AND MINUTE_FROM <= #18h AND MINUTE_TO >= #18h AND MINUTE_TO < #24h AND IS_ABSENT = 0 THEN (DATEDIFF(MINUTE, DATE_FROM, DATEADD(MINUTE, #18h, CAST(CAST(DATE_FROM AS DATE) AS DATETIME))) / 60.00) * (BRUTO_HOUR + #myCondition)

Answer 1

Use a simple CTE that returns all the columns of #tblALL_HOURS and the value returned by ISNULL function:
ISNULL(CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END,0)
as a column and then update With the CTE and use that column in place of the condition:
WITH cte AS (
SELECT *,
ISNULL(CASE WHEN IS_HOLIDAY = 1 THEN 2.5 * NETO_HOUR WHEN DAY_IN_WEEK = 'Sunday' THEN NETO_HOUR END,0) AS myCondition
FROM #tblALL_HOURS
)
UPDATE cte
SET REG_WORK_COST = CASE
WHEN MINUTE_FROM >= 0 AND MINUTE_FROM <= #6h AND MINUTE_TO >= #6h AND MINUTE_TO <= #18h AND IS_ABSENT = 0
THEN (DATEDIFF(MINUTE, DATEADD(MINUTE, #6h, CAST(CAST(DATE_TO AS DATE) AS DATETIME)), date_to)/60.00) * (BRUTO_HOUR + myCondition)
WHEN MINUTE_FROM >= 0 AND MINUTE_FROM <= #6h AND MINUTE_TO >= #18h AND MINUTE_TO < #24h AND IS_ABSENT = 0
THEN 12.00 * (BRUTO_HOUR + myCondition)
WHEN MINUTE_FROM >= #6h AND MINUTE_FROM <= #18h AND MINUTE_TO >= #6h AND MINUTE_TO <= #18h AND IS_ABSENT = 0
THEN (DATEDIFF(MINUTE, DATE_FROM, DATE_TO) / 60.00) * (BRUTO_HOUR + myCondition)
WHEN MINUTE_FROM >= #6h AND MINUTE_FROM <= #18h AND MINUTE_TO >= #18h AND MINUTE_TO < #24h AND IS_ABSENT = 0
THEN (DATEDIFF(MINUTE, DATE_FROM, DATEADD(MINUTE, #18h, CAST(CAST(DATE_FROM AS DATE) AS DATETIME))) / 60.00) * (BRUTO_HOUR + myCondition)
END