sql - SQL - 左连接中的表别名

Question

我正在尝试使用 Left Join 编写一个简单的 SQL 查询。

这是查询：

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
)

第二个表别名是 TOTAL_LINES。

运行它时，我收到 TOTAL_LINES 未列出的错误。

奇怪的是，当尝试自己运行第二个查询时，没有错误：

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

有人有线索吗？

Answer 1

希望您AS TOTAL_LINES在错误的位置分配表别名。

在第二个子查询之后放置表别名将解决您的问题。

你可以试试下面的查询：

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

尝试这个..

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;

Answer 3

TOTAL_LINES 必须是整个 select 的别名，而不是 from 子句中的 table。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)