sole method
Execute the query and get the first result if it's the sole matching record.
Implementation
Future<Map<String, dynamic>> sole() async {
_setStatement(Operator.get);
_buildSql();
var results = await db.select(_sql);
if (results.isNotEmpty && results.length == 1) {
return results[0];
} else {
return Map.of({});
}
}