@UNQKVSA[[u,]filename,"key","value"] : Append to the value of an existing UnQlite key/value pair.
|u||Optional flag that the key and value are Unicode (UTF16)|
|filename||Database opened with @UNQOPEN|
|key||Key to update|
|value||Value to append to the existing value|
Returns 0 if successful, or the error text if not.
This example opens a database named "test.db", appends a string to an existing value, and then reads it back.
echo Testing file write and read
echo %@unqkvs[test.db,"key1","Append this to the first value"]