您必须使用ORDER BY子句指定订单。在您的示例中，您可以执行以下操作：
SELECt 1 AS seq, COUNT(datediff(yyyy,dob,admitdate) as counts FROM myTable WHERe ...condition-1...UNIOnSELECt 2 AS seq, COUNT(datediff(yyyy,dob,admitdate) as counts FROM myTable WHERe ...condition-2... ORDER BY seq
