Question

I have the following table “test”,

Let the data in the table be as follows,

Now I want to select last entry (only date not the timestamp) for each day and corresponding value as two columns. one being the date and other being the value.

I am able to fetch only the date using the following query,

SELECT max( date( date ) ) AS date
FROM test
GROUP BY date( date )
LIMIT 0 , 30 

But am not being able to get the corresponding values for those dates.
How can I do it..? By googling, I came to know that I have to use join to achieve this, but again I couldn’t use join without any errors.

Answer 1

First change the column name from the reserved keyword date to something that doesn’t need quoting:

ALTER TABLE test
    CHANGE COLUMN `date` timestamp_entered TIMESTAMP NOT NULL
                         --- or some other sensible name

Then you could use:

SELECT
    grp.date_entered  
  , t.value 
FROM 
        test  AS t
    JOIN 
        ( SELECT 
            , DATE( timestamp_entered )  AS date_entered
              MAX( timestamp_entered )   AS max_timestamp
          FROM 
              test
          GROUP BY
              DATE( timestamp_entered )
        ) 
          AS grp 
      ON 
          grp.max_timestamp = t.timestamp_entered