difference

[mani14]

hello!
sorry, i don´t speak english.
hello again!
It what differs it is between these two sentence?
- exec (' exec sp_MShelpindexPru cliente,'+''+@indexid+''+'output')
-exec sp_MShelpindexPru cliente,@indexid output

Supposedly, they are equal , no?
None gives me mistake, but The first one does not give me a result And the second one gives me the correct result. Which is the difference between both?
I need to do it of the second form, because I need to insert one it use @dbname initially.
Thank you very much, and excuses me for my English.";

[rmiao]

Did you try
exec ('exec sp_MShelpindexPru cliente, @indexid output')

By the way, why do it this way at first place?