Collation problem

   I met a collation problem yesterday, When i create a backup table using a specific table script. But when i union the result set

with this two tables, A error message was pop, The collation is different between two table. But i think the script is same. why the collation is different. After i discussed with colleague I know the reason, because the original table was created on another server which the collation is different form the current one. So the collation of new created columns are different from the original

 one. Finally I unified the collation of new created columns by manual. The problem was resolved.