My Sql merging rows

问题

How can I query merge rows which has same dates and get rid of null

Date       | Long | Short
2006-07-06 | t1   |
2006-07-06 |      | t2
2006-07-05 | t1   | 
2006-07-05 |      | t2
2006-07-04 | t1   |
2006-07-04 |      | t2
2006-07-03 | t1   | 
2006-07-03 |      | t2

to this

Date       | Long | Short
2006-07-06 | t1   | t2
2006-07-05 | t1   | t2
2006-07-04 | t1   | t2
2006-07-03 | t1   | t2

回答1:

SELECT `date`, MAX(`long`) `long`, MAX(short) short
FROM yourtable
GROUP BY `date`

回答2:

One approach to getting the specified resultset, is using a GROUP BY and aggregate functions:

SELECT t.Date
     , MAX(t.Long) AS `Long`
     , MAX(t.Short) AS `Short`
  FROM mytable t
 GROUP
    BY t.Date

来源：https://stackoverflow.com/questions/17618143/my-sql-merging-rows