SQL-左聯接中的表別名

Question

我試圖用Left Join編寫一個簡單的SQL查詢。

這是查詢：

SELECT * 
FROM ( 
   SELECT * 
   FROM TRN_IN.COIT AS TRANSMISSIONS
     LEFT JOIN ( 
       SELECT TRNNumber ,COUNT(ID) 
       FROM TRN_IN.COIT AS TOTAL_LINES   
       WHERE DataPiece02 = 'TO'   
       GROUP BY TRNNumber 
   ) ON TRANSMISSIONS.TRNNumber  = TOTAL_LINES.TRNNumber
)

第二個表別名為TOTAL_LINES。

運行它時，出現錯誤，未列出TOTAL_LINES。

奇怪的是，當嘗試自行運行第二個查詢時，沒有錯誤：

(SELECT TRNNumber ,COUNT(ID) 
 FROM TRN_IN.COIT AS TOTAL_LINES 
 WHERE DataPiece02 = 'TO' 
 GROUP BY TRNNumber )

有人知道嗎？

Answer 1

希望您在錯誤的位置分配了AS TOTAL_LINES表別名。

在第二個子查詢之后放置表別名名稱將解決您的問題。

您可以嘗試以下查詢：

SELECT *
FROM (
    SELECT *
    FROM TRN_IN.COIT AS TRANSMISSIONS
    LEFT JOIN (
        SELECT TRNNumber
            ,COUNT(ID) AS CountDetails
        FROM TRN_IN.COIT 
        WHERE DataPiece02 = 'TO'
        GROUP BY TRNNumber
        ) AS TOTAL_LINES ON TRANSMISSIONS.TRNNumber = TOTAL_LINES.TRNNumber
    ) AS Result

Answer 2

TOTAL_LINES必須是整個select的別名，而不是from子句中的表。 改成：

SELECT * FROM ( SELECT * FROM TRN_IN.COIT AS TRANSMISSIONS

LEFT JOIN ( SELECT TRNNumber ,COUNT(ID) FROM TRN_IN.COIT WHERE DataPiece02 = 'TO'   GROUP BY TRNNumber ) AS TOTAL_LINES   

ON TRANSMISSIONS.TRNNumber  = TOTAL_LINES   .TRNNumber)

Answer 3

嘗試這個..

SELECT TOTAL_LINES.TRNNumber,COUNT(TOTAL_LINES.ID) FROM TRN_IN.COIT TRANSMISSIONS LEFT JOIN TRN_IN.COIT TOTAL_LINES 
ON TRANSMISSIONS.TRNNumber  = TOTAL_LINES.TRNNumber
WHERE TOTAL_LINES.DataPiece02 = 'TO'   GROUP BY TOTAL_LINES.TRNNumber;