Use the @STREQNULL function in the same way as @STREQ to determine whether or not two string (character) columns or literal strings are equal. However, if the two arguments passed to the function are NULL, then the return value is 1.
Syntax
@STREQNULL (string1, string2)
string1
The first column or literal string to be compared.
string2
The second column or literal string to be compared.