SQL計數加入

Question

我有這個疑問

SELECT semester, COUNT(id) AS total, RIGHT(RTRIM(semester), 4) AS year 
FROM TextbookReservation 
WHERE (semester IS NOT NULL) 
AND (semester <> '') 
AND (semester <> 'SM2008') 
AND semester <> 'SU2008') 
GROUP BY semester ORDER BY year, semester DESC 

將會產生這樣的：

semester total year 
SP2006 2277 2006 
FA2006 4367 2006 
SP2007 2893 2007 
FA2007 5624 2007 
SP2008 4083 2008 
FA2008 6451 2008 

我想回這樣的事：

year totalSpring totalFall 
2006 2277  4367 
2007 2893  5624 
2008 4083  6451 

任何想法關於如何處理這個查詢？謝謝！

Answer 1

沒有透視表，因爲你沒有指定版本：

SELECT [year], 
sum(case WHEN left(semester,2)='SP' then total ELSE 0 END) as totalSpring , 
sum(case WHEN left(semester,2)='FA' THEN total else 0 end) as totalFall 
from (

     SELECT semester 
      , count(id) AS total 
      , right(RTRIM(semester), 4) AS year 
     FROM 
      TextbookReservation 
     WHERE 
      semester IS NOT NULL 
      AND semester <> '' 
      AND semester <> 'SM2008' 
      AND semester <> 'SU2008' 
     GROUP BY 
      semester 
) t 
GROUP BY t.[year] 
order by t.[year] 

Answer 2

你想要做的是創建一個pivot。版本2005及更高版本的SQL具有內置命令來轉發數據。

您可以指定您的數據庫正在使用哪個版本的SQL Server？

PS。您還可以在2005年之前使用Case語句來做到這一點。因爲您的示例只有兩個不同的學期值，我將使用該方法提供答案。

Select year, SUM(TotalSpring), SUM(TotalFall) From 
(select RIGHT(RTRIM(semester), 4) AS year, case LEFT(semester,2) when 'SP' then 1 else 0 end TotalSpring, case LEFT(semester,2) when 'FA' then 1 else 0 end TotalFall 
from TextbookReservation 
WHERE (semester IS NOT NULL) 
AND (semester <> '') 
AND (semester <> 'SM2008') 
AND semester <> 'SU2008') as t1 
group by year 
order by year 

Answer 3

其他答案的簡化版：

SELECT 
    RIGHT(RTRIM(semester), 4) year, 
    COUNT(CASE WHEN left(semester,2)='SP' then id else null end) totalSpring, 
    COUNT(CASE WHEN left(semester,2)='FA' then id else null end) totalFall 
FROM TextbookReservation 
WHERE (semester IS NOT NULL) 
     AND (semester <> '') 
     AND (semester <> 'SM2008') 
     AND (semester <> 'SU2008') 
GROUP BY RIGHT(RTRIM(semester), 4) 
ORDER BY RIGHT(RTRIM(semester), 4) DESC 

這裏，測試腳本：

CREATE TABLE #TextbookReservation 
(
    semester VARCHAR(6), 
    id INT 
) 

INSERT INTO #TextbookReservation VALUES ('SP2006', 1) 
INSERT INTO #TextbookReservation VALUES ('SP2006', 2) 
INSERT INTO #TextbookReservation VALUES ('SP2006', 3) 
INSERT INTO #TextbookReservation VALUES ('SP2006', 4) 
INSERT INTO #TextbookReservation VALUES ('SP2006', 5) 
INSERT INTO #TextbookReservation VALUES ('FA2006', 1) 
INSERT INTO #TextbookReservation VALUES ('FA2006', 2) 
INSERT INTO #TextbookReservation VALUES ('FA2006', 3) 
INSERT INTO #TextbookReservation VALUES ('SP2007', 1) 
INSERT INTO #TextbookReservation VALUES ('SP2007', 2) 
INSERT INTO #TextbookReservation VALUES ('FA2007', 1) 
INSERT INTO #TextbookReservation VALUES ('FA2007', 2) 
INSERT INTO #TextbookReservation VALUES ('FA2007', 3) 
INSERT INTO #TextbookReservation VALUES ('FA2007', 4) 
INSERT INTO #TextbookReservation VALUES ('FA2007', 5) 

SELECT 
    RIGHT(RTRIM(semester), 4) year, 
    COUNT(CASE WHEN left(semester,2)='SP' then id else null end) totalSpring, 
    COUNT(CASE WHEN left(semester,2)='FA' then id else null end) totalFall 
FROM #TextbookReservation 
WHERE (semester IS NOT NULL) 
     AND (semester <> '') 
     AND (semester <> 'SM2008') 
     AND (semester <> 'SU2008') 
GROUP BY RIGHT(RTRIM(semester), 4) 
ORDER BY RIGHT(RTRIM(semester), 4) DESC 


DROP TABLE #TextbookReservation