'.' 附近的语法不正确在使用 Coalesce 时

Question

我正在尝试连接三个表，我成功连接了两个。

这有效（两个 Tables）

SELECT  ImportExportBadFile.ID, ImportExportSettingID,
    ImportExportBadFile.UserID,
    Coalesce(UserName,'') UserName  
    FROM
    ImportExportBadFile 
    LEFT OUTER JOIN Users HGSQLUsers ON ImportExportBadFile.UserID = HGSQLUsers.ID
    ORDER BY  ImportExportBadFile.DateTimeStamp DESC

UserName 属于 Users Table

现在，当我尝试添加另一个 Table:

SELECT  ImportExportBadFile.ID, ImportExportSettingID,
    SETT.Name,
    ImportExportBadFile.UserID,
    Coalesce(UserName,'') HGSQLUsers.UserName  
    FROM
    ImportExportBadFile 
    LEFT OUTER JOIN Users HGSQLUsers ON ImportExportBadFile.UserID = HGSQLUsers.ID
    INNER JOIN ImportExportSettings SETT ON ImportExportBadFile.ImportExportSettingID = SETT.ID  
    ORDER BY  ImportExportBadFile.DateTimeStamp DESC

It gives Error : "Incorrect syntax near '.'." at line : "Coalesce(UserName,'') HGSQLUsers.UserName"

如果我只写 UserName 它给出

"Ambiguous column name 'UserName'."

求助。

Answer 1

可能 UserName 列存在于两个 table 中，您需要指定 table 想要从中获取 UserName，如下所示

SELECT  ImportExportBadFile.ID, ImportExportSettingID,
    SETT.Name,
    ImportExportBadFile.UserID,
    Coalesce( HGSQLUsers.UserName  ,'') as "HGSQLUsers.UserName"
    FROM
    ImportExportBadFile 
    LEFT OUTER JOIN Users HGSQLUsers ON ImportExportBadFile.UserID = HGSQLUsers.ID
    INNER JOIN ImportExportSettings SETT ON ImportExportBadFile.ImportExportSettingID = SETT.ID
ORDER BY  ImportExportBadFile.DateTimeStamp DESC

错误 "Incorrect syntax near '.'." at line : 来自别名 HGSQLUsers.UserName 您可以使用它，但要有配额。

我还建议您为每个 table 使用别名，如下所示 - 对我来说更具可读性

SELECT  I.ID, I.ImportExportSettingID,
        SETT.Name,
        I.UserID,
       Coalesce( HGSQLUsers .UserName  ,'') as "HGSQLUsers.UserName"
FROM ImportExportBadFile I
LEFT OUTER JOIN Users HGSQLUsers ON I.UserID = HGSQLUsers.ID
INNER JOIN ImportExportSettings SETT ON I.ImportExportSettingID = SETT.ID  
ORDER BY  I.DateTimeStamp DESC

Answer 2

实际上这对我来说在反复试验中很有效：

SELECT  ImportExportBadFile.ID, ImportExportSettingID,
    SETT.Name,
    ImportExportBadFile.UserID,
    Coalesce(HGSQLUsers.UserName,'')
    FROM
    ImportExportBadFile 
    INNER JOIN ImportExportSettings SETT ON ImportExportBadFile.ImportExportSettingID = SETT.ID  
    LEFT OUTER JOIN Users HGSQLUsers ON ImportExportBadFile.UserID = HGSQLUsers.ID
    ORDER BY  ImportExportBadFile.DateTimeStamp DESC

但@Parado 的回答更具体和解释。

谢谢。

'.' 附近的语法不正确在使用 Coalesce 时

Incorrect syntax near '.' while using Coalesce

sql

sql-server

sql-server-2008

coalesce