How to Resolve 'Ambiguous Column Name' Errors in SQL Queries?

Ambiguous Column Name in SQL Query: Resolving InvoiceID Issue

The error message "ambiguous column name" in SQL queries arises when attempting to access columns with duplicate names from multiple joined tables. To resolve this ambiguity, it's crucial to specify the table from which the column is being selected.

In the provided query, the error occurs with the InvoiceID column, which exists in both the Invoices and InvoiceLineItems tables. To resolve this, modify the query as follows:

SELECT VendorName, Invoices.InvoiceID, InvoiceSequence, InvoiceLineItemAmount
FROM Vendors 
JOIN Invoices ON (Vendors.VendorID = Invoices.VendorID)
JOIN InvoiceLineItems ON (Invoices.InvoiceID = InvoiceLineItems.InvoiceID)
WHERE Invoices.InvoiceID IN
    (SELECT InvoiceSequence FROM InvoiceLineItems WHERE InvoiceSequence > 1)
ORDER BY VendorName, Invoices.InvoiceID, InvoiceSequence, InvoiceLineItemAmount

By specifying the "Invoices" table prefix before "InvoiceID," the query explicitly indicates that the column should be retrieved from the Invoices table. This resolves the ambiguity and allows SQL Server Management Studio (SSMS) to correctly retrieve and display the VendorID column.

Remember to specify the table prefix for all ambiguous columns to avoid this error when querying data from multiple tables.

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