Problem with Renaming a Column in SQL Server

Understanding the Issue and Solution

Renaming columns in a SQL Server table can be a straightforward process, but it requires attention to detail and understanding of how SQL Server handles column names. In this article, we will delve into the problem of renaming a column in SQL Server and provide the solution to resolve this issue.

Background Information

SQL Server stores column names in a system-defined data type called sysname, which is essentially a string data type that can hold up to 128 characters. When you create a table or column, SQL Server automatically generates a unique name for it. This name is stored in the sys.columns system view and can be queried using the sys.columns system view.

When you try to rename a column using the sp_rename stored procedure, SQL Server checks if the new name already exists as a column in the table. If it does, SQL Server raises an error with message “Msg 15248, Level 11, State 1: Either the parameter @objname is ambiguous or the claimed @objtype (COLUMN) is wrong.” This error occurs because the @objname parameter of the sp_rename stored procedure contains a column name that might not be unique.

Understanding SQL Server’s Column Naming Convention

The Issue with Column Names

SQL Server uses a convention for quoting identifiers, which includes column names. When you use double quotes (") to quote an identifier, it is treated as a literal identifier and not affected by the QUOTED_IDENTIFIER setting of the session.

However, when you use square brackets ([]) to quote an identifier, it is subject to the QUOTED_IDENTIFIER setting of the session. If QUOTED_IDENTIFIER is set to ON, square brackets are treated as literal identifiers and can be used in column names.

In this case, the issue lies in the fact that SQL Server treats double quotes (") as a special character when quoting an identifier, whereas it treats square brackets ([]) as the standard quotation mark for quoted identifiers. This difference leads to confusion when renaming columns using the sp_rename stored procedure.

Resolving the Issue

The Correct Syntax

To rename a column in SQL Server, you need to use the correct syntax and attention to detail. Here are the steps:

1. Use Double Quotes: When quoting an identifier that contains special characters (such as double quotes " or single quotes ’ ), it should be enclosed in square brackets []. However, for simple column names without special characters, we can simply enclose them in double quotes.

2. Check for Existing Column Names: Before renaming a column, you need to check if the new name already exists as a column in the table. You can use the sys.columns system view or query the INFORMATION_SCHEMA.COLUMNS system view to achieve this.

3. Use QUOTED_IDENTIFIER Setting: If you are using the sp_rename stored procedure with square brackets ([]) to quote an identifier, ensure that QUOTED_IDENTIFIER is set to ON for your session.

Here’s how to rename a column in SQL Server:

• Initial Table

CREATE TABLE AllocationDetails ( Conversion_Fee_Per_Share FLOAT )

*   Faulty Rename
    ```markdown
EXEC sp_rename
  'dbo.AllocationDetails.[Conversion_Fee_Per_Share]',
  '[Conversion_Fee]',
  'COLUMN'

• Fixed Rename

EXEC sp_rename ‘dbo.AllocationDetails."[Conversion_Fee]"’, ‘Conversion_Fee’, ‘COLUMN’

    Alternatively, you can use the following syntax to rename a column using `sp_rename` with double quotes:

        ```markdown
EXEC sp_rename
  'dbo.AllocationDetails.[Conversion_Fee]',
  'Conversion_Fee',
  'COLUMN'

• Drop Table

DROP TABLE AllocationDetails 

Additional Considerations

Best Practices for Column Naming Conventions

SQL Server recommends that you use meaningful and descriptive names for your columns. Here are some best practices to consider:

• Use double quotes (") when quoting column names, unless you’re using square brackets ([]).
• Avoid special characters in column names.
• Ensure consistency in your naming convention throughout the database.

By following these guidelines and being mindful of SQL Server’s column naming conventions, you can effectively rename columns in your table without encountering errors like “Msg 15248, Level 11, State 1: Either the parameter @objname is ambiguous or the claimed @objtype (COLUMN) is wrong.”

Last modified on 2023-09-28