Question

我在SQL Server 2016中只有一个查询示例：编写SQL代码，它将显示表InvoiceNumber中包含值的值INVOICE ............ ..

我需要加入3个表格。这是我的代码：

SELECT 
    InvoiceNumber
FROM 
    INVOICE AS I 
INNER JOIN 
    LINE_ITEM AS LI ON (I.InvoiceNumber = LI.InvoiceNumber)
INNER JOIN 
    PRODUCT AS P ON (LI.ProductNumber = P.ProductNumber)
WHERE 
    Description = 'Heather Sweeney Seminar Live in Dakkas on 25-OCT-09 - Video'

并且此代码总是会导致错误：

不明确的列名InvoiceNumber

WHERE查询

中的SELECT子句

Answer 1

始终限定查询中的所有列名称，尤其是当它具有多个表时：

SELECT I.InvoiceNumber
FROM INVOICE AS I INNER JOIN
     LINE_ITEM AS LI
     ON I.InvoiceNumber = LI.InvoiceNumber INNER JOIN
     PRODUCT P
     ON LI.ProductNumber = P.ProductNumber
WHERE P.Description = 'Heather Sweeney Seminar Live in Dakkas on 25-OCT-09 - Video'

如果你养成这种习惯，你就不会有这样的错误。

Answer 2

如果2个表具有相同的列，则必须在查询中告诉您要使用哪个列。通过在它前面添加表名来做到这一点。

SELECT I.InvoiceNumber FROM INVOICE AS I ...

关于“不明确的列名”的错误

2 个答案: