Is Ambiguous column name a SQL Server only error

Question

I'm looking at a SQL tutorial and the command that the tutorial gave gives me an error on my SQL Server Management Studio of "Ambiguous column name". Is this error only applicable when using SQL server?

question from:https://stackoverflow.com/questions/65868024/is-ambiguous-column-name-a-sql-server-only-error

Answer 1

No, not at all. In reality, a column reference in SQL should always be qualified -- meaning that it should say what table it comes from. You can think of the unqualified names as a short-hand. The SQL engine does the favor of figuring out the table when it can. And when a column is in multiple tables, it cannot figure it out.

Your queries should be readable and unambiguous. In your case, your code should look something like this:

select c.cname
from college c join
     apply a
     on c.cname = a.cname
where c.enrollment > 2000 and a.major = 'CS';

Note: This is guessing where enrollment and major are coming from, because there is not enough information in your query to figure this out.

Also, this uses proper, explicit, standard, readable JOIN syntax. Never use commas in the FROM clause, even if your course/tutorial materials do so. In fact, that alone suggests that they are way out-of-date (decades old).

Also, use table aliases (the abbreviations) so queries are simpler to write and to read.