Friday, September 9, 2011

Query Error when using ORDER BY if the column and * is in the SELECT list


Suppose, you have a query where you get one column explicitly and all other columns using * then you get an Ambiguous column name error.
The following query results in an error:
SELECT Title,* FROM HumanResources.Employee ORDER BY Title

Msg 209, Level 16, State 1, Line 1
Ambiguous column name 'Title'.

The following does not give an error:
SELECT Title,* FROM HumanResources.Employee

So whats’s the solution?
Adding an alias for the table and using alias with the column in ORDER BY or providing a fully qualified path to the column in ORDER BY will fix this issue.

One of the following query will fix this issue.
SELECT Title,* FROM HumanResources.Employee e ORDER BY e.Title
SELECT Title,* FROM HumanResources.Employee ORDER BY HumanResources.Employee.Title

If the Title column was not in SELECT list, the issue would not arise. The following query works perfectly:
SELECT * FROM HumanResources.Employee ORDER BY Title

Also, if you didn’t have * in your select, but just specific list of columns, then also you do not need to have alias in order by
SELECT EmployeeID,Title FROM HumanResources.Employee ORDER BY Title

So, it’s only when you have a combination of explicit column name and a * in the SELECT you get this issue.

Weird issue or the way syntax is expected by SQL. However, you have to live by some quirks which creates jobs for DB programmers.

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