Release 10.1A: OpenEdge Data Management:
DataServer for Microsoft SQL Server

> ## Zero-length character strings

> When you use the Unknown value (`?`) in a `WHERE` clause with the DataServer, the Unknown value (`?`) satisfies only the equals (=) or not equal (<>) operator. You can also use a zero-length character string in a `WHERE` clause. The Unknown value (`?`) and zero-length character string are not the same. The Unknown value (`?`) translates to a `NULL`, which is a special marker in a data source that supports `NULL`s used to represent missing information. On the other hand, zero-length strings and blank columns contain actual values. Both of the following statements find the first `customer` record with a zero-length string in the `address2` field. Notice the space between the quotation marks in the first statement:

>     FIND FIRST customer WHERE address2 = " ".
>     FIND FIRST customer WHERE address2 = "".

> Although “” and “ ” evaluate the same way in a `WHERE` clause, they have different results when you use them with the `BEGINS` function. For example, the following statement retrieves all `customer` `names` except those that have the Unknown value (`?`):

>     FOR EACH customer WHERE names BEGINS "":

> The following statement uses “ ” to retrieve only those names that begin with a space:

>     FOR EACH customer WHERE names BEGINS " ":

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