在SQL

Question

我无法从下面列出的输入数据到输出数据中找出SQL的枢纽。

这是我的输入数据。

State   MONTH   YEAR    CNT
---------------------------
NY  MAR 2019    1
CA  MAR 2018    3
CA  JAN 2019    7
VA  APR 2018    1
VA  APR 2019    2
AZ  APR 2019    4
AZ  MAY 2019    5

输出数据：

2018        2019            
state   MAR APR JAN MAR APR MAY
AZ                  4   5
CA  3       7           
NY              1       
VA      1           2

Answer 1

对于SQL SERVER-您可以尝试执行此操作，尽管它将在不同的行中返回YEARS。

SELECT State,YEAR,
ISNULL(JAN,0) JAN,
ISNULL(FEB,0) FEB,
ISNULL(MAR,0) MAR,
ISNULL(APR,0) APR,
ISNULL(MAY,0) MAY
FROM 
(
    SELECT
    State,
    YEAR,
    MONTH, 
    CNT
    FROM your_table
) as s
PIVOT
(
    SUM(CNT) 
    FOR MONTH IN ([MAR],[FEB],[JAN],[APR],[MAY])
) PVT
ORDER BY 2,1

Answer 2

您可以使用条件聚合：

select state,
       sum(case when month = 'MAR' and year = 2018 then cnt end) as 2018_MAR,
       sum(case when month = 'APR' and year = 2018 then cnt end) as 2018_APR,
       sum(case when month = 'JAN' and year = 2019 then cnt end) as 2019_JAN,
       sum(case when month = 'MAR' and year = 2019 then cnt end) as 2019_MAR,
       sum(case when month = 'APR' and year = 2019 then cnt end) as 2019_APR,
       sum(case when month = 'MAY' and year = 2019 then cnt end) as 2019_MAY
from t
group by state;