MySql按日期对2个或更多表进行排序

Question

I have the following tables:

comments:
id   /   comments    /   date
1        comment1     1389986953
2        comment2     1389986935


topics:
id   /   topics    /   date
1        topic1      1389986930
2        topic2      1389986940

How can i select all the rows from both tables and sort them by the date? so it will look something like:

topic1
comment2
topic2
comment1

Answer 1

Try a SELECT UNION

Reference: http://dev.mysql.com/doc/refman/5.0/en/union.html

(SELECT comments AS col, date FROM comments)
UNION
(SELECT topics AS col, date FROM topics)
ORDER BY date;

Answer 2

You will want to use UNION ALL to combine the results of both tables, then wrap this to sort.

SELECT a.type 
FROM   (SELECT comments AS type, 
               date 
        FROM   comments 
        UNION ALL 
        SELECT topics, 
               date 
        FROM   topics) a 
ORDER  BY a.date; 

Answer 3

SELECT * FROM
    (SELECT comments AS mergedField, date
    FROM comments
    UNION ALL
    SELECT topics, date
    FROM topics) mergeTable
ORDER BY date ASC