Question

I am looking through a stored procedure and seeing many lines like:

case when len(isnull(INVOICE.INVOICE_DATE,'')) > 0 
      and isdate(INVOICE.INVOICE_DATE) = 1 
    then convert(datetime,INVOICE.INVOICE_DATE)
    else null end

and

case when len(isnull(SHIPMENT.NET_AMOUNT_DUE,'')) > 0 
      and isnumeric(SHIPMENT.NET_AMOUNT_DUE) = 1
   then convert(money,SHIPMENT.NET_AMOUNT_DUE) 
   else null end

I don’t understand why the ISNULL and LEN checks are always there. Is there some benefit that I am missing? Conversely, is there any detriment to how the code is currently written?

Answer 1

The LEN and ISNULL checks are not needed.

ISDATE and ISNUMERIC will return a 0 if the value is NULL or empty, so this is just not needed. Possibly someone being extra extra cautious…

These can be written as:

case when ISDATE(INVOICE.INVOICE_DATE) = 1 
    then convert(datetime,INVOICE.INVOICE_DATE)
    else null end

And:

case when ISNUMERIC(SHIPMENT.NET_AMOUNT_DUE) = 1
   then convert(money,SHIPMENT.NET_AMOUNT_DUE) 
   else null end