MySQL Orderby a number, Nulls last

问题:

Currently I am doing a very basic OrderBy in my statement.

SELECT * FROM tablename WHERE visible=1 ORDER BY position ASC, id DESC

The problem with this is that NULL entries for \'position\' are treated as 0. Therefore all entries with position as NULL appear before those with 1,2,3,4. eg:

NULL, NULL, NULL, 1, 2, 3, 4

Is there a way to achieve the following ordering:

1, 2, 3, 4, NULL, NULL, NULL.

回答1:

MySQL has an undocumented syntax to sort nulls last. Place a minus sign (-) before the column name and switch the ASC to DESC:

SELECT * FROM tablename WHERE visible=1 ORDER BY -position DESC, id DESC

It is essentially the inverse of position DESC placing the NULL values last but otherwise the same as position ASC.

A good reference is here http://troels.arvin.dk/db/rdbms#select-order_by

回答2:

I found this to be a good solution for the most part:

SELECT * FROM table ORDER BY ISNULL(field), field ASC;

回答3:

Something like

SELECT * FROM tablename where visible=1 ORDER BY COALESCE(position, 999999999) ASC, id DESC

Replace 999999999 with what ever the max value for the field is

回答4:

NULL LAST

SELECT * FROM table_name ORDER BY id IS NULL, id ASC

回答5:

Try using this query:

SELECT * FROM tablename
WHERE visible=1 
ORDER BY 
CASE WHEN position IS NULL THEN 1 ELSE 0 END ASC,id DESC

回答6:

You can coalesce your NULLs in the ORDER BY statement:

select * from tablename
where <conditions>
order by
    coalesce(position, 0) ASC, 
    id DESC

If you want the NULLs to sort on the bottom, try coalesce(position, 100000). (Make the second number bigger than all of the other position\'s in the db.)

回答7:

SELECT * FROM tablename WHERE visible=1 ORDER BY CASE WHEN `position` = 0 THEN \'a\' END , position ASC

回答8:

You can swap out instances of NULL with a different value to sort them first (like 0 or -1) or last (a large number or a letter)...

SELECT field1, IF(field2 IS NULL, 9999, field2) as ordered_field2
  FROM tablename
 WHERE visible = 1
 ORDER BY ordered_field2 ASC, id DESC

回答9:

For a DATE column you can use:

---

NULLS last:

ORDER BY IFNULL(`myDate`, \'9999-12-31\') ASC

Blanks last:

ORDER BY IF(`myDate` = \'\', \'9999-12-31\', `myDate`) ASC

回答10:

Why don\'t you order by NULLS LAST?

SELECT * 
FROM tablename
WHERE visible = 1 
ORDER BY position ASC NULLS LAST, id DESC