使用Join和where子句計算語句

Question

前兩個是單獨的結果..第三個是我試圖加入另一個表的語句。我的問題是我無法在sql語句中設置條件。 在最后一個連接語句中，我得到了兩個帶有Route Id的列和帶有Flab = 1的和，但是我無法設置flag = 0的條件..請幫助我需要T2作為最后一列。

Answer 1

SELECT a.RouteCode, 
       SUM(CASE WHEN b.ScheduledFlag = '1' THEN 1 ELSE 0 END) AS T1,
       SUM(CASE WHEN b.ScheduledFlag = '0' THEN 1 ELSE 0 END) AS T2
FROM Routes a inner join CustomerVisits as b on a.RouteCode = b.RouteCode
WHERE b.RouteStartDate = '12/15/2011' 
and a.DepotCode = '6'
group by a.RouteCode

請注意，根據數據庫連接的區域設置，您的日期格式字符串可能不明確。 使用類似ODBC規范的區域設置安全日期格式（ yyyy-mm-dd hh:mi:ss ）

Answer 2

一種方法是分別創建每個計數查詢，然后從每個計數查詢執行左連接，這樣如果兩個計數表中都沒有匹配，則不會過濾結果。

SELECT q1.routecode,
       t1,
       t2
FROM   routes
       LEFT JOIN (SELECT routecode,
                         COUNT(routecode) AS t1
                  FROM   customervisits
                  WHERE  ( routecode IN ( '701', '702', '704', '703', '705' ) )
                         AND routestartdate = '12/15/2011'
                         AND schelduledflag = '1'
                  GROUP  BY routecode) AS q1
         ON routes.routecode = q1.routecode
       LEFT JOIN (SELECT routecode,
                         COUNT(routecode) AS t2
                  FROM   customervisits
                  WHERE  ( routecode IN ( '701', '702', '704', '703', '705' ) )
                         AND routestartdate = '12/15/2011'
                         AND schelduledflag = '0'
                  GROUP  BY routecode) AS q2
         ON routes.routecode = q2.routecode
WHERE  a.depotcode = '6'  and (t1 is not null or t2 is not null);