Union All 查询顺序混乱

将多个select 语句使用 Union All 联合后，查询结果并未次序显示。例如：

sql1:

select * from t where type=1 order by id;
sql2:

select * from t where type=2 order by id;

sql3:

select * from t where type=3 order by id;

sql1 union all sql2 union all sql3;
sql1、sql2和sql3分别查询的时候是正确的，union all 后顺序就打乱了，怎么才能让他保持原来的顺序呢？即：先显示sql1的结果集，再显示sql2的结果集，然后显示sql3

本人这样解决的：在三个sql中都加入临时列，别名Sort_index，值依次递增，如下：

sql1:

select 1 Sort_index,* from t where type=1 order by id;
sql2:

select 2 Sort_index,* from t where type=2 order by id;

sql3:

select 3 Sort_index,* from t where type=3 order by id;

之后在外层加入Order by Sort_index，如下：

select * from (sql1 union all sql2 union all sql3) order by Sort_index;

执行结果顺序显示。