Problem

Given a table with two columns, write a SQL query to find the number of distinct values in each column.
Input:
| Column1 | Column2 |
|---------|---------|
| 1       | 2       |
| 2       | 3       |
| 3       | 4       |
| 4       | 5       |
Output:
| Column1 | Column2 |
|---------|---------|
| 4       | 5       |

Solution

SELECT COUNT(DISTINCT Column1) AS Column1, COUNT(DISTINCT Column2) AS Column2
FROM table;

/*

The solution above is optimal because it uses the COUNT function with the DISTINCT keyword. This will count the number of unique values in each column.

*/