Question

Ho threre. When I run a simple select on some tables like:

SELECT
    ValidoDa, 
    Tab_Ticket_Default,
    * 
FROM 
    Dipendente_Stor
WHERE 
    CodiceAbi = '08753' and 
    Matricola = 98
order by 
     ValidoDa 

I can get the error “Ambiguous column name ‘ValidoDa'”

What is the reason? There is only one filed called ValidoDa!

can you explain this behaviour?

Answer 1

ORDER BY will first attempt to resolves SELECT column list.

In this case, you have ValidoDa twice therefore it is ambiguous

You can fix it like this with an alias, but SELECT * is bad practice anyway

SELECT
    ValidoDa AS ValidoDaFOO, 
    Tab_Ticket_Default,
    * 
FROM 
    Dipendente_Stor
WHERE 
    CodiceAbi = '08753' and 
    Matricola = 98
order by 
     ValidoDa 
     -- or ValidoDaFOO