# Best approach to map day of date in bulk

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We need to map the Date field so that every date value is the first of the month. The value mapper tile can do this one at a time, but we need to do this in bulk. Can anyone recommend the best approach using a function?

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`Date` - INTERVAL (DATOFMONTH(`Date`) - 1) DAY

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Should be DAYOFMONTH

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`Date` - INTERVAL (DATOFMONTH(`Date`) - 1) DAY

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I'm getting an 'unknown function:DATOFMONTH' error in my ETL preview on this @GrantSmith I tried `Date` - INTERVAL (DATEOFMONTH(`Date`) - 1) DAY in case there was a typo on DATE, but still get 'unknown function'

As a workaround I used Date Function to extract Month of Date and the function below

CASE

WHEN MONTH(`Date`) = 1 then '1/1/2022'

WHEN MONTH(`Date`) = 2 then '2/1/2022'

WHEN MONTH(`Date`) = 3 then '3/1/2022'

WHEN MONTH(`Date`) = 4 then '4/1/2022'

WHEN MONTH(`Date`) = 5 then '5/1/2022'

WHEN MONTH(`Date`) = 6 then '6/1/2022'

WHEN MONTH(`Date`) = 7 then '7/1/2022'

WHEN MONTH(`Date`) = 8 then '8/1/2022'

WHEN MONTH(`Date`) = 9 then '9/1/2022'

WHEN MONTH(`Date`) = 10 then '10/1/2022'

WHEN MONTH(`Date`) = 11 then '11/1/2022'

WHEN MONTH(`Date`) = 12 then '12/1/2022'

end

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