# Sorting of NULL Values

### Sorting of NULL Values

NULL values introduce a problem with sorting, and the various SQL products handle the ordering of NULL values in different ways. You should consult the relevant SQL manuals for more details. Four options exist:

• NULL values are always presented first, regardless of whether the ordering is ascending or descending.

• NULL values are always presented last, regardless of whether the ordering is ascending or descending.

• NULL values are seen as the lowest values.

• NULL values are seen as the highest values.

MySQL treats NULL values as the lowest values in a column. Therefore, they are always placed at the bottom of the result if the order is descending and at the top if the order is ascending; see the following example and the accompanying result.

##### 11. Get the different league numbers, and sort the result in descending order.

 ```SELECT DISTINCT LEAGUENO FROM PLAYERS ORDER BY 1 DESC ``` The result is: ```LEAGUENO -------- 8467 7060 6524 6409 2983 2513 2411 1608 1319 1124 ? ```

 Exercise 12.1: Show at least three different ORDER BY clauses that would sort the PLAYERS table in ascending order by player number. Exercise 12.2: Indicate which of the following SELECT statements are incorrect: ```SELECT * FROM PLAYERS ORDER BY 2 ``` ```SELECT * FROM PLAYERS ORDER BY 20 DESC ``` ```SELECT PLAYERNO, NAME, INITIALS FROM PLAYERS ORDER BY 2, INITIALS DESC, 3 ASC ``` ```SELECT * FROM PLAYERS ORDER BY 1, PLAYERNO DESC ``` Exercise 12.3: For each match, get the player number, the team number, and the difference between the number of sets won and the number of sets lost; order the result in ascending order on this difference.