SQL：Select 给定日期时间的每一天的最后一条记录

Question

I have a table of stock data (the db is MySQL):

trade_time          price  
2013-01-02 09:43:00 515.61
2013-01-03 09:39:00 525.90
2013-01-03 11:38:00 539.44
2013-01-03 13:22:00 509.16
2013-01-04 09:47:00 507.40
2013-01-04 14:33:00 517.45
2013-01-07 09:33:00 550.42
2013-01-07 13:13:00 524.85
2013-01-07 14:51:00 536.44

I would like to return the last traded price for each day

trade_date price  
2013-01-02 515.61
2013-01-03 509.16
2013-01-04 517.45
2013-01-07 536.44

What makes this question different from other "selecting the latest record based on datetime" questions on this site is that input is in datetime but output is in date . Let me know this question has already been answered.

Answer 1

You may join to a subquery which finds the maximum datetime for each date.

SELECT t1.trade_time, t1.price
FROM yourTable t1
INNER JOIN
(
    SELECT DATE(trade_time) AS trade_date, MAX(trade_time) AS max_trade_time
    FROM yourTable
    GROUP BY DATE(trade_time)
) t2
    ON t2.trade_date = DATE(t1.trade_time) AND
       t2.max_trade_time = t1.trade_time
ORDER BY
    t1.trade_time;

Demo

Answer 2

Here is an efficient solution using window function ROW_NUMBER() over a type cast of the timestamp column to date:

select trade_date, price
from (
    select trade_date, price, row_number() over
        (partition by date(trade_date) 
         order by trade_date desc) as row_num 
    from stock) as subquery
where row_num = 1
order by trade_date

Answer 3

You can use a correlated subquery:

select t.*
from t
where t.trade_date = (select max(t2.trade_date)
                      from t t2
                      where date(t2.trade_date) = date(t.trade_date)
                     );

Answer 4

I understand this is an implementation in MY-SQL , but I tried in SQL-Server just for fun and this query gives the requisite output:

SELECT CAST(SQ.TT AS DATE) AS TRADED_DATE, PRICE
FROM STOCK
INNER JOIN
(SELECT MAX(TRADE_TIME) AS TT
FROM STOCK
GROUP BY CAST(TRADE_TIME AS DATE)) SQ
ON SQ.TT = TRADE_TIME

Output as

TRADED_DATE PRICE
----------- ---------------------------------------
2013-01-02  515.61
2013-01-03  509.16
2013-01-04  517.45
2013-01-07  536.44

(4 rows affected)