Question: I am trying to find a way to print the result taking into account if exists records in a table or not.
If yes I should print all the records in a table, otherwise I should print only one record.

**Example:**

I have the Table Example:

| ColA | Colb | ColC |
| --- | --- | --- |

If select count(\*) from Example > 0 THEN Return

| ColA | Colb | ColC |
| --- | --- | --- |
| 1 | VA1 | NULL |
| 2 | VB1 | NULL |
| 3 | NULL | VA2 |

If select count(\*) from Example <= 0 THEN Return

| ColA | Colb | ColC |
| --- | --- | --- |
| Result | NA | NA |

Is it possible to do something like that? I am doing the development using PRESTO.

Thanks you in advance

Answer: 
Try:

```
SELECT ColA,ColB,ColC
FROM Example
union
SELECT 
   'Result' as ColA,
   'NA' as ColB,
   'NA' as ColC
WHERE NOT EXISTS (SELECT ColA,ColB,ColC
                  FROM Example)

```

It is not needed to select the 3 columns in the sub-query, but currently I copy/pasted the query. It can be replaced by `SELECT 1` or `SELECT NULL` (which is a matter of taste...)
We could introduce a dummy/default row via a union, and then retain it only in the event of the `Example` table being empty:

```sql
 WITH cte AS (
    SELECT ColA, ColB, ColC, 0 AS pos FROM Example
    UNION ALL
    SELECT 'Result', 'NA, 'NA', 1
)

SELECT ColA, ColB, ColC
FROM cte
WHERE pos = 0 OR NOT EXISTS (SELECT 1 FROM cte WHERE pos = 0);

```