Why does this AND function not work and a simplified version do?

[sallierie]

Hi there,

I dont understand the difference between 2 formulas :

IF(
    AND(
        {Startdatum Leverancier (rol repowered)} != BLANK(),
        {Einddatum leverancier (rol repowered)} = BLANK()
    ),
    "OT",
    IF(
        AND(
            {Startdatum Leverancier (rol repowered)} = BLANK(),
            {Einddatum leverancier (rol repowered)} = BLANK()
        ),
        "",
        "BT"
    )
)

This formula does  NOT work as intended and ALWAYS shows OT regardless of the 2 fields content (empty or filled). I need to add that these fields are date fields. 

IF(
    {Startdatum Leverancier (rol repowered)} = BLANK(), 
    "", 
    IF(
        {Einddatum leverancier (rol repowered)} = BLANK(), 
        "OT", 
        "BT"
    )
)

This one DOES work as intended. Although I fixed the issue my curiousity is getting the better of me what I did wrong in the first bit of code. Anybody ideas? 

[BillH]

see https://support.airtable.com/docs/identifying-blank-values#:~:text=The%20BLANK()%20function%20can,is....

"Note

When using BLANK() along with != (not equal to), you may receive unexpected results if the fields you are selecting aren't numeric."

[Alexey_Gusev]

Hi.
Airtable formulas are quite flexible. You don't need to use BLANK. Statement 'if value X exists, show Z, otherwise show Y' will be IF(X,Z,Y)
You can even omit 'value if false', the default is 'show nothing' : if(X,Z)

therefore, you can do it in such way:

IF({Startdatum Leverancier (rol repowered)},
  IF({Einddatum leverancier (rol repowered)},'BT','OT'))