How to check if 1 Product SKU (not key column) already exist in Table

[DatVi]

Hi community, I have a question about how to add a formula for Valid If in data validity to check if that product SKU already exist (not key column), If yes, an Invalid value error will appear and not allow me to add new data. If not, so let me add a new row.

By the way, it still allows me to edit that row if necessary.

Thanks

[Joseph_Seddik · Accepted solution]

ISBLANK(FILTER("tableName", [SKU] = [_ThisRow].[SKU]) - LIST([_ThisRow]))

[DatVi]

It does not check whether does SKU already exist or not

[Joseph_Seddik]

Try Then Tell

[DatVi]

Appreciate it, thanks, the expression after works correctly.