Question

I have a column, it’s time is ‘DATETIME’. I want to output it in the order of timeline, but when I use ORDER BY create_time DESC, ‘2011-09-10 16:16:04’ is behind ‘2011-07-16 03:20:01’.

Seems it is treating datatime column as string.

How can I handle this without changing the column type?

UPDATE:

This is part of my query:

SELECT 'bookcomment' AS type
            ,b.book_id
            ,b.name
            ,c.book_id
            ,c.author_id
            ,c.content
            ,c.create_time as create_time
            ,u.id
            ,u.name
            FROM tbl_book AS b,
                        tbl_book_comment AS c,
                        tbl_user AS u
            WHERE u.id=c.author_id in (1,2) AND b.book_id=c.book_id

UNION ALL

SELECT 'bookreview' AS type
            ,b.book_id
            ,b.name
            ,re.book_id
            ,re.author_id
            ,re.content
            ,re.create_time as create_time
            ,u.id
            ,u.name
            FROM tbl_book AS b,
                        tbl_book_review AS re,
                        tbl_user AS u
            WHERE u.id=re.author_id in (1,2) AND b.book_id=re.book_id

UNION ALL
...
            ORDER BY create_time DESC

And part of the output:

array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "Whatever" ["author_id"]=> string(4) "test" ["content"]=> string(19) "2011-07-16 03:20:01" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }
array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "whatever" ["author_id"]=> string(13) "sdfwefwaefwea" ["content"]=> string(19) "2011-05-11 03:33:33" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }
array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "whatever" ["author_id"]=> string(5) "test0" ["content"]=> string(19) "2011-09-10 16:16:04" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }
array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "whatever" ["author_id"]=> string(5) "test1" ["content"]=> string(19) "2011-09-10 16:16:04" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }
array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "whatever" ["author_id"]=> string(5) "test2" ["content"]=> string(19) "2011-09-10 16:16:04" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }
array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "whatever" ["author_id"]=> string(5) "test3" ["content"]=> string(19) "2011-09-10 16:16:04" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }
array(7) { ["type"]=> string(16) "new post comment" ["book_id"]=> string(1) "1" ["name"]=> string(9) "whatever" ["author_id"]=> string(5) "test4" ["content"]=> string(19) "2011-09-10 16:16:04" ["create_time"]=> string(1) "3" ["id"]=> string(1) "1" }

Answer 1

You appear to have the data in the wrong columns. In your output sample create_time is 3 for all of them, so the order is undefined. Double-check data is in the right columns?