Operations and functions handle arguments with a NULL value conforming to SQL rules. There is one exception to the STRING data type. NULL string and empty string are considered equal. As a result, null string arguments are handled as empty (zero length) strings.

Example:

The following are legal comparisons that give a non-null Boolean result:

"abc" == NULL
"abc" > NULL

Respectively, they are analogous to the following comparisons:

"abc" == ""
"abc" > ""

However, in SQL, both of these expressions result in a NULL (UNKNOWN) value.