使用SELECT结果制作表

Question

我有一张这样的表：

我想执行以下SELECT语句：

SELECT count(*) from table WHERE A=1 and date between 2013-02 and 2013-03
SELECT count(*) from table WHERE A=1 and date between 2013-03 and 2013-04
SELECT count(*) from table WHERE A=1 and date between 2013-04 and 2013-05
....
SELECT count(*) from table WHERE B=1 and date between 2013-02 and 2013-03
SELECT count(*) from table WHERE B=1 and date between 2013-03 and 2013-04
SELECT count(*) from table WHERE B=1 and date between 2013-04 and 2013-05
...etc

什么是最快的查询，我可以将结果安排在如下表格中：

date    |A=1  |B=1  |C=1  |...
2013-Feb|count|count|count|
2013-Mar|count|...

Answer 1

SELECT DATE_FORMAT(date, '%Y-%m'),
       SUM(CASE WHEN A=1 THEN 1 END) AS Acount,
       SUM(CASE WHEN B=1 THEN 1 END) AS Bcount,
       SUM(CASE WHEN C=1 THEN 1 END) AS Ccount,
       SUM(CASE WHEN D=1 THEN 1 END) AS Dcount,
       SUM(CASE WHEN E=1 THEN 1 END) AS Ecount
FROM table
GROUP BY DATE_FORMAT(date, '%Y-%m')

如果A到E列中的唯一值为0或1（或可能是NULL），那么我们可以简化为：

SELECT DATE_FORMAT(date, '%Y-%m'),
       SUM(A) AS Acount,
       SUM(B) AS Bcount,
       SUM(C) AS Ccount,
       SUM(D) AS Dcount,
       SUM(E) AS Ecount
FROM table
GROUP BY DATE_FORMAT(date, '%Y-%m')

Answer 2

嗨，您可以拥有 GROUP BY 功能

    SELECT 
    to_char(date,'YYYY-MM') as date,
    CASE WHEN A=1 THEN COUNT(A)  END as A ,
    CASE WHEN B=1 THEN COUNT(B)  END as B ,
    CASE WHEN C=1 THEN COUNT(C)  END as C ,
    CASE WHEN D=1 THEN COUNT(D)  END as D ,
    CASE WHEN E=1 THEN COUNT(E)  END as E  
    from table_name group by date order by date

此查询根据年份和月份对列进行分组，并为您提供结果