Prevent duplicate recordings

[fon1]

If this column is used as a datetime, how to set it not to duplicate it?

Now is the date of attendance column is date time from the first date is date only.
At first I used The column titled First Name-Last Name Date of Attendance is the key.

using the formula
Valid If formula for colum :
NOT(IN([_THIS], SELECT(Time stamp[employee ID], [attendance date] = TODAY())))

Error_Message_If_Invalid : “You are registered. can’t repost”

But today I tried to repeat it. It did. From the usual studies in this group and groups. It cannot be re-recorded.

Want to record the date of attendance, 1 entry per day per person or code

The main columns are as follows:

1. Code
2. Name - Surname
3. Date of attendance (date time) press enter from user setting and press action save
4. The date of the event (date time), use the press action to now.

[Steve]

Maybe this instead?

NOT(
  IN(
    [_THIS],
    SELECT(
      Time stamp[attendance date],
      ([employee ID] = USEREMAIL())
    )
  )
)

[fon1]

It can still be recorded repeatedly.

[fon1]

The previous old formula that will use Not-In

ISBLANK(
FILTER(
“Down time”,
AND(
([Date of attendance] <> [_THISROW].[Date of attendance]),
([unique-column] = [_THISROW].[unique-column])
)
)
)