Question

I want to update all rows when invoiceID is NULL else update only the rows where all invoiceID‘s are the same.

My current SQL statement is as follows:

UPDATE Table SET strPOnummer = '123' 
WHERE strPOnummer = '456' AND strPOnummer != '' AND strPOnummer IS NOT NULL

So, when Table.invoiceID is NULL, it should update all rows, else update only the rows where invoiceID is the same.

Answer 1

Assuming that invoiceID is an input parameter, you could do this:

UPDATE Table 
SET strPOnummer = '123' 
WHERE --your non-invoiceID filtering conditions go here 
  AND (Table.invoiceID = @InvoiceID OR @InvoiceID IS NULL)

In this case if the @InvoiceID parameter is not null then the first condition will have to be met as the second will never be met, but if it is null then each row of the table will be matched by the second part of the condition and thus the first one isn’t relevant anymore