Say I have two tables with the following data:

```
A1
| c1 | c2 |
| a  | b  |

A2
| c1 | c2 |
| c  | d  |

```

I would like to run a select returning the data of both tables, with A1 data above A2 data:

```
A1 U A2
| c1 | c2 |
| a  | b  |
| c  | d  |

```

So on Hive I could do something like:

```
SELECT * FROM A1
UNION ALL
SELECT * FROM A2

```

But that does not produce the correct results. How could I enforce the order that the UNION ALL happens? Or would be another solution to produce this output?