MySQL按日期和計數分組

Question

我有如下表格：

借助MySql查詢，我想要的結果如下：

date        total    read    unread
2018-01-31   8        4        4
2018-02-01   2        2        0

Answer 1

嘗試這個：

SELECT date, COUNT(*) as total,
SUM(CASE WHEN read = 1 THEN 1 ELSE 0) as read
SUM(CASE WHEN read = 0 THEN 1 ELSE 0) as unread
FROM yourtable
GROUP BY date

Answer 2

您可以使用案例匯總過濾后的值以供讀取

select date
, count(*), sum(case when  read=1 then 1 else 0 end )  as read
, sum(case when  read=0 then 1 else 0 end )  as unread
from my_table 
group by date 

Answer 3

嘗試此操作在read列中不需要大小寫，因為1表示已read因此我們只求sum即可。 如果我們處理大量數據，它將對性能有所幫助：

SELECT date, 
    COUNT(*) as total,
    SUM(read) as read --Case not needed here
    SUM(CASE WHEN read = 0 THEN 1 ELSE 0) as unread
FROM yourtable
GROUP BY date

Answer 4

您必須使用group by by將日期group by行group by ，然后可以使用count來計數每個日期組內的總行數（=總列）。 為了獲得已讀和未讀的數量，可以將已讀和未讀的值sum

        SELECT date
             , COUNT(*) AS total
             , SUM(READ) AS READ
             , SUM(CASE WHEN READ = 0 THEN 1 ELSE 0 END) AS unread
        FROM mytable
        GROUP BY date