validation form entry

[yousseflf9]

i want when i type a name in a field to validate it by loocking if it's already exist or no in my table if it exist it warn me by text , if anyone got the formula for this validation

[cairoberts]

Hiya, try something like this?

COUNT(SELECT(TableName[ColumnName],[ColumnName]=[_THIS]))<2

[yousseflf9]

didn't work brother

[yousseflf9 · Accepted solution]

This expression works for me :

ISBLANK(FILTER("table name", ([column name] = [_THIS])) - LIST([_THIS]))